Segment Information (Reconciliation of Revenue from Segments to Consolidated) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenues	$ 2,697,413us-gaap_Revenues	$ 2,716,588us-gaap_Revenues	$ 2,833,020us-gaap_Revenues	$ 2,657,173us-gaap_Revenues	$ 2,736,794us-gaap_Revenues	$ 2,389,815us-gaap_Revenues	$ 2,590,642us-gaap_Revenues	$ 2,601,102us-gaap_Revenues	$ 10,904,194us-gaap_Revenues	$ 10,318,353us-gaap_Revenues	$ 9,840,911us-gaap_Revenues
US Traditional Segment Reporting Information [Member]
Segment Reporting Information [Line Items]
Revenues									5,283,268	5,115,941	4,881,994
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting Information [Line Items]
Revenues									1,014,143	962,818	876,119
Canada Segment Reporting Information [Member]
Segment Reporting Information [Line Items]
Revenues									1,181,865	1,185,017	1,140,264
Europe [Member]
Segment Reporting Information [Line Items]
Revenues									1,557,847	1,305,012	1,275,074
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Revenues									1,756,718	1,610,626	1,557,283
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Revenues									$ 110,353	$ 138,939	$ 110,177