Segment Information (Long-lived assets by Geographic Location) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Property and equipment, net of accumulated depreciation	$ 172,621	$ 166,636
United States
Segment Reporting Information [Line Items]
Property and equipment, net of accumulated depreciation	126,050	104,939
Europe
Segment Reporting Information [Line Items]
Property and equipment, net of accumulated depreciation	27,001	39,976
Other Geographic Locations
Segment Reporting Information [Line Items]
Property and equipment, net of accumulated depreciation	$ 19,570	$ 21,721