Segment Information (Revenues by geographic region) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues, net	$ 648,023	$ 634,646	$ 2,078,757	$ 2,026,057
United States
Segment Reporting Information [Line Items]
Revenues, net	504,732	499,316	1,653,342	1,616,453
Europe
Segment Reporting Information [Line Items]
Revenues, net	91,447	93,356	278,198	290,879
Other Geographic Locations
Segment Reporting Information [Line Items]
Revenues, net	$ 51,844	$ 41,974	$ 147,217	$ 118,725