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, 2021
Dec. 31, 2020
Mar. 31, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust $ 10,574 $ 10,295    
Marketable debt securities, available-for-sale 201,425 206,031    
Deferred consideration 13,742 15,248    
Deferred compensation liability 8,273 8,287    
Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 134,494 158,258    
Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 66,931 47,773    
U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 69,240 75,970    
U.S. Treasuries [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 22,521 3,641    
U.S. Government Sponsored Entities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 11,454 32,447    
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 debt securities, available-for-sale 1,045 1,152    
Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 53,800 49,841    
Corporate debt securities [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 36,869 36,287    
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 debt securities, available-for-sale 6,496 6,693    
Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 171,909 167,670    
Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 134,494 158,258    
Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 66,931 47,773    
Recurring [Member] | Commercial Paper [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 3,899 9,399    
Recurring [Member] | Money market funds [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 168,010 158,271    
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 10,574 10,295    
Recurring [Member] | U.S. Treasuries [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 69,240 75,970    
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 debt securities, available-for-sale 22,521 3,641    
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 debt securities, available-for-sale 11,454 32,447    
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 debt securities, available-for-sale 1,045 1,152    
Recurring [Member] | Corporate debt securities [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 53,800 49,841    
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 debt securities, available-for-sale 36,869 36,287    
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 debt securities, available-for-sale 6,496 6,693    
Level 1 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 168,010 158,271    
Deferred consideration 0 0    
Deferred compensation liability 8,273 8,287    
Level 1 [Member] | Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 69,240 75,970    
Level 1 [Member] | Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 22,521 3,641    
Level 1 [Member] | Recurring [Member] | Commercial Paper [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 168,010 158,271    
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 debt securities, available-for-sale 69,240 75,970    
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 debt securities, available-for-sale 22,521 3,641    
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 debt 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 debt 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 debt 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 debt 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 debt securities, available-for-sale 0 0    
Level 2 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 3,899 9,399    
Deferred consideration 13,742 15,248    
Deferred compensation liability 0 0    
Level 2 [Member] | Recurring [Member] | Short-term investments [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 65,254 82,288    
Level 2 [Member] | Recurring [Member] | Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 44,410 44,132    
Level 2 [Member] | Recurring [Member] | Commercial Paper [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 3,899 9,399    
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 10,574 10,295    
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 debt 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 debt 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 debt securities, available-for-sale 11,454 32,447    
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 debt securities, available-for-sale 1,045 1,152    
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 debt securities, available-for-sale 53,800 49,841    
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 debt securities, available-for-sale 36,869 36,287    
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 debt securities, available-for-sale 6,496 6,693    
Level 3 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 0    
Deferred consideration 0 0    
Deferred compensation liability 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 debt 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 debt securities, available-for-sale 0 0    
Level 3 [Member] | Recurring [Member] | Commercial Paper [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 debt 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 debt 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 debt 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 debt 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 debt 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 debt 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 debt securities, available-for-sale 0 0    
Contingent Consideration [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Contingent consideration 5,301 5,572 $ 3,162 $ 3,387
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 $ 5,301 $ 5,572