Income Taxes - Schedule of Domestic and Foreign Components of Loss before Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
United States	$ (32,112)	$ (24,285)	$ (40,845)
Foreign	(93,910)	(45,349)	(16,760)
Total	$ (126,022)	$ (69,634)	$ (57,605)