Annual report pursuant to Section 13 and 15(d)

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

v3.20.4
Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets held in rabbi trust $ 10,295 $ 9,452  
Marketable debt securities, available-for-sale 206,031 211,561  
Deferred consideration 15,248 1,390  
Deferred compensation liability 8,287 8,241  
Short-term investments [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Marketable debt securities, available-for-sale 158,258 150,752  
Long-term marketable securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Marketable debt securities, available-for-sale 47,773 60,809  
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 75,970 124,580  
U.S. Treasuries [Member] | Long-term marketable securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Marketable debt securities, available-for-sale 3,641 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 debt securities, available-for-sale 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 1,152 1,355  
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 49,841 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 debt securities, available-for-sale 36,287 26,471  
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 6,693 8,560  
Recurring [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash and cash equivalents 167,670 190,600  
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 158,258 150,752  
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 47,773 60,809  
Recurring [Member] | Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash and cash equivalents 9,399 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 158,271 185,513  
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 10,295 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 debt securities, available-for-sale 75,970 124,580  
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 debt securities, available-for-sale 3,641 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 debt securities, available-for-sale 32,447 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 debt securities, available-for-sale 1,152 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 debt securities, available-for-sale 49,841 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 debt securities, available-for-sale 36,287 26,471  
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 6,693 8,560  
Level 1 [Member] | Recurring [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Cash and cash equivalents 158,271 185,513  
Deferred consideration 0 0  
Deferred compensation liability 8,287 8,241  
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 75,970 121,580  
Level 1 [Member] | Recurring [Member] | Long-term marketable securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Marketable debt securities, available-for-sale 3,641 24,423  
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 158,271 185,513  
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 debt securities, available-for-sale 75,970 124,580  
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 debt securities, available-for-sale 3,641 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 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 9,399 5,087  
Deferred consideration 15,248 1,390  
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 82,288 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 debt securities, available-for-sale 44,132 36,386  
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 9,399 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 10,295 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 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 32,447 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 debt securities, available-for-sale 1,152 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 debt securities, available-for-sale 49,841 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 debt securities, available-for-sale 36,287 26,471  
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 6,693 8,560  
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 5,572 3,387 $ 1,474
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 $ 5,572 $ 3,387