Goodwill and Intangible Assets - Aggregate amortization expense (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 31,232	$ 22,160	$ 73,207