Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail)

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Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Mar. 31, 2020
Dec. 31, 2019
Mar. 31, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust $ 7,992 $ 9,452    
Marketable securities, available for sale 189,074 211,561    
Deferred compensation liability 7,244 8,241    
Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 143,864 150,752    
Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 45,210 60,809    
U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 114,720 124,580    
U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 10,510 24,423    
U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 9,137 0    
U.S. Government Sponsored Entities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 1,328 1,355    
Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 19,711 26,172    
Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 25,606 26,471    
Asset-backed securities and other [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 296      
Asset-backed securities and other [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 7,766 8,560    
Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 156,267 190,600    
Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 143,864 150,752    
Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 45,210 60,809    
Recurring [Member] | Commercial Paper and Other [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 9,498 5,087    
Recurring [Member] | Money market funds [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 146,769 185,513    
Recurring [Member] | Assets held in rabbi trust [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust 7,992 9,452    
Recurring [Member] | U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 114,720 124,580    
Recurring [Member] | U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 10,510 24,423    
Recurring [Member] | U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 9,137 0    
Recurring [Member] | U.S. Government Sponsored Entities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 1,328 1,355    
Recurring [Member] | Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 19,711 26,172    
Recurring [Member] | Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 25,606 26,471    
Recurring [Member] | Asset-backed securities and other [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 296 0    
Recurring [Member] | Asset-backed securities and other [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 7,766 8,560    
Level 1 [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Deferred compensation liability 7,244 8,241    
Level 1 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 146,769 185,513    
Level 1 [Member] | Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 114,720 124,580    
Level 1 [Member] | Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 10,510 24,423    
Level 1 [Member] | Recurring [Member] | Commercial Paper and Other [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Level 1 [Member] | Recurring [Member] | Money market funds [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 146,769 185,513    
Level 1 [Member] | Recurring [Member] | Assets held in rabbi trust [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust 0 0    
Level 1 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 114,720 124,580    
Level 1 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 10,510 24,423    
Level 1 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 1 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 1 [Member] | Recurring [Member] | Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 1 [Member] | Recurring [Member] | Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 1 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 1 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 2 [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Deferred compensation liability 0 0    
Level 2 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 9,498 5,087    
Level 2 [Member] | Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 29,144 26,172    
Level 2 [Member] | Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 34,700 36,386    
Level 2 [Member] | Recurring [Member] | Commercial Paper and Other [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 9,498 5,087    
Level 2 [Member] | Recurring [Member] | Money market funds [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Level 2 [Member] | Recurring [Member] | Assets held in rabbi trust [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust 7,992 9,452    
Level 2 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 2 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 2 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 9,137 0    
Level 2 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 1,328 1,355    
Level 2 [Member] | Recurring [Member] | Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 19,711 26,172    
Level 2 [Member] | Recurring [Member] | Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 25,606 26,471    
Level 2 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 296 0    
Level 2 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 7,766 8,560    
Level 3 [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Deferred compensation liability 0 0    
Level 3 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Level 3 [Member] | Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Commercial Paper and Other [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Level 3 [Member] | Recurring [Member] | Money market funds [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Level 3 [Member] | Recurring [Member] | Assets held in rabbi trust [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust 0 0    
Level 3 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | U.S. Government Sponsored Entities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Level 3 [Member] | Recurring [Member] | Asset-backed securities and other [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable securities, available for sale 0 0    
Contingent Consideration [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Contingent consideration 3,162 3,387 $ 2,923 $ 2,875
Contingent Consideration [Member] | Level 1 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Contingent consideration 0 0    
Contingent Consideration [Member] | Level 2 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Contingent consideration 0 0    
Contingent Consideration [Member] | Level 3 [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Contingent consideration $ 3,162 $ 3,387