Segment Information (Summary Of Financial Information By Geographic Location) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 2,547,834	$ 2,534,156	$ 2,644,894	$ 2,598,610	$ 2,622,692	$ 2,702,488	$ 2,608,101	$ 2,448,372	$ 10,325,494	$ 10,381,653	$ 9,047,657
Long-lived assets	298,414				277,645				298,414	277,645	253,630
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									8,917,732	8,874,820	7,792,728
Long-lived assets	293,915				272,555				293,915	272,555	248,331
Foreign countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									1,407,762	1,506,833	1,254,929
Long-lived assets	$ 4,499				$ 5,090				$ 4,499	$ 5,090	$ 5,299