Segment Reporting and Major Customers - Property and Equipment, net (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	$ 363,336	$ 325,218
United States
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	304,186	273,690
Europe
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	46,895	43,586
Other
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	$ 12,255	$ 7,942