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Fair Value Measurements - Schedule of Assets and Liabilities at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Jun. 30, 2021 | Dec. 31, 2020 | Jun. 30, 2020 | Dec. 31, 2019
--- | --- | --- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets held in rabbi trust | $ 11,178 | $ 10,295 |  |
Marketable debt securities, available-for-sale | 244,686 | 206,031 |  |
Deferred consideration | 11,998 | 15,248 |  |
Deferred compensation liability | 8,346 | 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 | 147,172 | 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 | 97,514 | 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 | 74,436 | 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 | 52,196 | 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 |  | 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 | 913 | 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 | 72,736 | 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 | 37,649 | 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 | 6,756 | 6,693 |  |
Recurring [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and cash equivalents | 169,241 | 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 | 147,172 | 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 | 97,514 | 47,773 |  |
Recurring [Member] | Commercial Paper [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and cash equivalents | 1,800 | 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 | 167,441 | 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 | 11,178 | 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 | 74,436 | 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 | 52,196 | 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 | 0 | 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 | 913 | 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 | 72,736 | 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 | 37,649 | 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 | 6,756 | 6,693 |  |
Level 1 [Member] | Recurring [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Cash and cash equivalents | 167,441 | 158,271 |  |
Deferred consideration | 0 | 0 |  |
Deferred compensation liability | 8,346 | 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 | 74,436 | 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 | 52,196 | 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 | 167,441 | 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 | 74,436 | 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 | 52,196 | 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 | 1,800 | 9,399 |  |
Deferred consideration | 11,998 | 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 | 72,736 | 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 | 45,318 | 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 | 1,800 | 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 | 11,178 | 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 | 913 | 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 | 72,736 | 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 | 37,649 | 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 | 6,756 | 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 | 6,817 | 5,572 | $ 5,208 | $ 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 | $ 6,817 | $ 5,572 |  |

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