Segment Information (Reconciliation of Revenue from Segments to Consolidated) (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
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 2,828,591	$ 2,438,634	$ 2,630,340	$ 2,520,613	$ 2,697,413	$ 2,716,588	$ 2,833,020	$ 2,657,173	$ 10,418,178	$ 10,904,194	$ 10,318,353
US Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									5,465,026	5,283,268	5,115,941
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									643,865	1,014,143	962,818
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									6,108,891	6,297,411	6,078,759
Canada Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									45,034	28,350	26,171
Canada Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,023,012	1,153,515	1,158,846
Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,068,046	1,181,865	1,185,017
EMEA Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,190,742	1,235,049	1,129,657
EMEA Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									286,666	322,798	175,355
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,477,408	1,557,847	1,305,012
Asia Pacific Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,638,357	1,686,436	1,524,543
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									56,581	70,282	86,083
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,694,938	1,756,718	1,610,626
Corporate Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$ 68,895	$ 110,353	$ 138,939