Property and Equipment, net - Depreciation and Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Line Items]
Depreciation and amortization expense	$ 7,381	$ 6,095	$ 20,759	$ 17,997
Depreciation and Amortization
Property, Plant and Equipment [Line Items]
Effect of the foreign exchange gains upon settlement of cash flow hedges	$ (33)	$ 125	$ 160	$ 282