Segment and Geographic Information Schedule of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues from External Customers and Long-Lived Assets
Revenue	$ 3,122,378	$ 2,465,800	$ 8,873,893	$ 7,267,054
UNITED STATES
Revenues from External Customers and Long-Lived Assets
Revenue	1,535,557	1,395,495	4,716,927	4,268,600
UNITED KINGDOM
Revenues from External Customers and Long-Lived Assets
Revenue	408,474	399,155	1,294,155	1,171,829
GERMANY
Revenues from External Customers and Long-Lived Assets
Revenue	415,748	549	564,698	862
Other countries
Revenues from External Customers and Long-Lived Assets
Revenue	$ 762,599	$ 670,601	$ 2,298,113	$ 1,825,763