Assets and Liabilities Measured at Fair Value - Components by Hierarchy Level (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Assets:
Fair value of assets	$ 236,491	$ 324,055
Liabilities:
Contingent consideration payable	26,296	25,825
Deferred compensation plan liability	3,946	4,078
Fair value of liabilities	30,242	29,903
Commercial paper
Assets:
Fair value of assets	151,307	217,095
Asset-backed securities
Assets:
Fair value of assets	13,716	9,438
Corporate debt securities
Assets:
Fair value of assets	20,932	39,513
U.S. government agency bonds
Assets:
Fair value of assets	46,240	53,582
Money market funds
Assets:
Fair value of assets	4,296	4,427
Level 2
Assets:
Fair value of assets	236,491	324,055
Liabilities:
Contingent consideration payable	0	0
Deferred compensation plan liability	3,946	4,078
Fair value of liabilities	3,946	4,078
Fair value of the Convertible Notes	4,500
Level 2 \| Commercial paper
Assets:
Fair value of assets	151,307	217,095
Level 2 \| Asset-backed securities
Assets:
Fair value of assets	13,716	9,438
Level 2 \| Corporate debt securities
Assets:
Fair value of assets	20,932	39,513
Level 2 \| U.S. government agency bonds
Assets:
Fair value of assets	46,240	53,582
Level 2 \| Money market funds
Assets:
Fair value of assets	4,296	4,427
Level 3
Liabilities:
Contingent consideration payable	26,296	25,825
Deferred compensation plan liability	0	0
Fair value of liabilities	$ 26,296	$ 25,825

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 30
-Section 35
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

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Fair value of financial and nonfinancial obligations.

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