Fair Value Measurements (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Increase (decrease) in fair value of Symphony Icon, Inc. purchase liability	$ 2,101	$ (703)	$ 5,927
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings	2,101	(703)	5,927
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	(21,013)	(3,200)	(750)
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	$ 0	$ 18,912	$ 22,815	$ 17,638