Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in fair value of contingent consideration	$ 12,200	$ (700)	$ 4,300	$ 2,300
Contingent consideration liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	55,900	71,200	63,800	78,200
Change in fair value	12,200	(700)	4,300	2,300
Transfers out of Level 3 fair value hierarchy	(15,000)	0	(15,000)	0
Settlements	0	0	0	(10,000)
Balance at end of period	53,100	$ 70,500	$ 53,100	$ 70,500
Change in fair value of contingent consideration	$ 10,000