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
Sep. 30, 2021
Dec. 31, 2020
Sep. 30, 2020
Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Assets held in rabbi trust $ 11,056 $ 10,295    
Marketable debt securities, available-for-sale 247,404 206,031    
Deferred consideration 11,227 15,248    
Deferred compensation liability 7,962 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 116,902 158,258    
Long-term marketable securities [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Marketable debt securities, available-for-sale 130,502 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 19,991 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 87,057 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 0 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 822 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 96,911 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 35,234 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 7,389 6,693    
Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 223,678 167,670    
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 116,902 158,258    
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 130,502 47,773    
Recurring [Member] | Commercial Paper [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 0 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 223,678 158,271    
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 11,056 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 19,991 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 87,057 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   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 822 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 96,911 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 35,234 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 7,389 6,693    
Level 1 [Member] | Recurring [Member]        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash and cash equivalents 223,678 158,271    
Deferred consideration 0 0    
Deferred compensation liability 7,962 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 19,991 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 87,057 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 223,678 158,271    
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 19,991 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 87,057 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 0 9,399    
Deferred consideration 11,227 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 96,911 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 43,445 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 0 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 11,056 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 0 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 822 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 96,911 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 35,234 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 7,389 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 8,098 5,572 $ 4,683 $ 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 $ 8,098 $ 5,572