Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Amortization expense – cost of revenue	$ 8,824	$ 4,164	$ 4,712
Amortization expense – operating expenses	12,096	8,251	7,611
Total amortization expense	$ 20,920	$ 12,415	$ 12,323