Fair Value Measurement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent Earn-out Liability	$ 26,300	$ 17,300	$ 47,400	$ 27,000
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances		17,300
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss)	$ 9,000	$ (47,400)	$ 20,400