Segment Information (Revenues by geographic region) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Revenues, net	$ 740,823	$ 720,189
United States
Segment Reporting Information [Line Items]
Revenues, net	586,568	600,055
Europe
Segment Reporting Information [Line Items]
Revenues, net	86,264	78,675
Other Geographic Locations
Segment Reporting Information [Line Items]
Revenues, net	$ 67,991	$ 41,459