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Fair Value Measurements - Summary of Reconciliation of Recurring Fair Value Measurements (Detail) - Deferred Consideration Obligation [Member] - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
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Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |  |
Beginning balance | $ 175,300 | $ 157,147 | $ 173,024 | $ 161,540
Net realized losses/(gains) | 4,063 | 3,110 | 7,823 | 6,208
Net unrealized losses/(gains) | 23,358 | 4,037 | 25,556 | (367)
Settlements | (3,937) | (3,021) | (7,619) | (6,108)
Ending balance | $ 198,784 | $ 161,273 | $ 198,784 | $ 161,273

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- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References 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 (c)(2) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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- Definition Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References 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 (c) -URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258 + Details
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