Fair Value Measurements - Fair Value of Contingent Consideration Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2019				$ 176,500					$ 176,500
Increase in fair value of contingent consideration	$ 500	$ 1,800	$ 9,200	$ 1,600	$ 1,500	$ 2,959	$ 0	$ 0	13,100	$ 4,459	$ 0
Balance at December 31, 2020	$ 189,600				$ 176,500				$ 189,600	$ 176,500