Fair Value Measurements - Fair Value of Contingent Consideration Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2019			$ 176,500
Increase in fair value of contingent payments	$ 1,800	$ 2,959	12,600	$ 2,959
Balance at September 30, 2020	$ 189,100		$ 189,100