Segment Reporting and Major Customers - Property and Equipment, net (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	$ 373,868	$ 383,074
United States
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	312,707	321,119
Europe
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	46,466	45,872
Other
Property and equipment, net, by geographic areas
Property and equipment, net of accumulated depreciation and amortization	$ 14,695	$ 16,083