Fair Value Measurements - Level 3 Contingent Purchase Price (Details) - Contingent Purchase Price Liability - Fair Value, Measurements, Recurring - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 111,171	$ 118,571	$ 137,289	$ 123,757
Payments	(40,616)	(1,564)	(62,618)	(8,811)
Fair value adjustments to contingent purchase prices included in net loss	(7,672)	12,403	(11,788)	14,464
Balance at end of period	$ 62,883	$ 129,410	$ 62,883	$ 129,410