Assets and Liabilities Measured at Fair Value - Components by Hierarchy Level (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Fair value of assets	$ 301,957	$ 314,270
Liabilities:
Contingent consideration payable	25,361	22,681
Deferred compensation plan liability	3,585	4,419
Fair value of liabilities	28,946	27,100
Commercial paper
Assets:
Fair value of assets	195,054	73,710
Asset-backed securities
Assets:
Fair value of assets	16,602	77,810
Corporate debt securities
Assets:
Fair value of assets	66,110	145,991
U.S. government agency bonds
Assets:
Fair value of assets	20,284	11,991
Money market funds
Assets:
Fair value of assets	3,907	4,768
Level 2
Assets:
Fair value of assets	301,957	314,270
Liabilities:
Contingent consideration payable	0	0
Deferred compensation plan liability	3,585	4,419
Fair value of liabilities	3,585	4,419
Fair value of the Convertible Notes	6,900
Level 2 \| Commercial paper
Assets:
Fair value of assets	195,054	73,710
Level 2 \| Asset-backed securities
Assets:
Fair value of assets	16,602	77,810
Level 2 \| Corporate debt securities
Assets:
Fair value of assets	66,110	145,991
Level 2 \| U.S. government agency bonds
Assets:
Fair value of assets	20,284	11,991
Level 2 \| Money market funds
Assets:
Fair value of assets	3,907	4,768
Level 3
Liabilities:
Contingent consideration payable	25,361	22,681
Deferred compensation plan liability	0	0
Fair value of liabilities	$ 25,361	$ 22,681

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)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-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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