Fair Value Measurements - Liability Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Contingent Consideration - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 57,477	$ 69,100	$ 55,750	$ 76,709
Contingent consideration expense	$ 1,115	$ (4,356)	$ 3,322	$ 884
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit	us-gaap:BusinessCombinationContingentConsiderationArrangementsContingentConsiderationBenefit
Contingent payments made	$ (10,090)	$ (130)	$ (10,579)	$ (12,991)
Effect of foreign exchange	(19)	51	(10)	63
Ending balance	$ 48,483	$ 64,665	$ 48,483	$ 64,665