Segment Information (Reconciliation of Revenue from Segments to Consolidated) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 3,069,298	$ 2,900,577	$ 3,039,068	$ 2,512,568	$ 2,828,591	$ 2,438,634	$ 2,630,340	$ 2,520,613	$ 11,521,511	$ 10,418,178	$ 10,904,194
US Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									5,964,968	5,465,026	5,283,268
US Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									840,446	643,865	1,014,143
Americas [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									6,805,414	6,108,891	6,297,411
Canada Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									46,938	45,034	28,350
Canada Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,118,004	1,023,012	1,153,515
Canada Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,164,942	1,068,046	1,181,865
EMEA Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,195,149	1,190,742	1,235,049
EMEA Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									340,518	286,666	322,798
EMEA [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,535,667	1,477,408	1,557,847
Asia Pacific Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,771,150	1,638,357	1,686,436
Asia Pacific Non-Traditional Segment Reporting Information [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									63,382	56,581	70,282
Asia Pacific [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									1,834,532	1,694,938	1,756,718
Corporate Segment [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues									$ 180,956	$ 68,895	$ 110,353