Fair Value Measurements (Details 1) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Business Combination, Contingent Consideration, Liability	$ 94,729,000	$ 122,426,000
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance of contingent payments	119,086,000	224,754,000
Payments	54,947,000	110,234,000
Additions	12,816,000	0
Redemption value adjustments	16,276,000	3,273,000
Foreign translation adjustment	(22,000)	1,293,000
Ending balance of contingent payments	93,209,000	119,086,000
Fixed payments [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Business Combination, Contingent Consideration, Liability	$ 1,520,000	3,340,000
Common Class A [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Restricted stock grant date fair value		$ 3,353,939