Fair Value Measurements - Reconciliation of Liabilities Measured at Fair Value Using Significant Unobservable Inputs (Details) - Level 3 - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Contingent consideration liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 71,200	$ 76,900	$ 78,200	$ 76,900
Change in fair value	(700)	(2,500)	2,300	(2,500)
Settlements	0	0	(10,000)	0
Balance at end of period	70,500	74,400	70,500	74,400
Common stock warrant liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	646	495	343	512
Change in fair value	(145)	48	158	31
Balance at end of period	$ 501	$ 543	$ 501	$ 543