Debt (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Short-term Debt, Weighted Average Interest Rate	1.49%	2.27%
Long-term debt:
Commercial paper	$ 465,803	$ 353,090
Global revolving credit facility	500	8,924
Unsecured U.S. notes - Medium-term notes	2,971,376	2,971,313
Unsecured U.S. obligations, principally bank term loans	55,500	105,500
Unsecured foreign obligations	295,055	313,406
Capital lease obligations	41,430	42,018
Total before fair market value adjustment	3,829,664	3,794,251
Fair market value adjustment on notes subject to hedging	13,944	16,725
Total after fair market value adjustment	3,843,608	3,810,976
Current portion of long-term debt, including capital leases	(257,718)	(358,155)
Long-term debt	3,585,890	3,452,821
Total debt	3,845,623	3,820,796
U.S Commercial Paper, Long-Term [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	0.35%	0.41%
Maturity date range, end	Jun. 08, 2016
Commercial paper	457,942	329,925
Canadian Commerial Paper [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	1.15%	1.14%
Maturity date range, end	Jun. 08, 2016
Commercial paper	$ 7,861	$ 23,165
Global Revolving Credit Facility Member
Long-term debt:
Long-term debt, Weighted Average Interest Rate	1.40%	1.58%
Maturity date range, end	Jun. 08, 2016
Unsecured U.S. notes - Medium-term notes, Long-Term [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	3.95%	4.01%
Maturity date range, start	Mar. 01, 2014
Maturity date range, end	Feb. 25, 2025
Unsecured U.S. obligations, principally bank term loans, Long-Term [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	1.49%	1.56%
Maturity date range, start	Mar. 08, 2015
Maturity date range, end	Mar. 19, 2019
Unsecured Foreign Obligations, Long-Term [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	1.92%	1.91%
Maturity date range, start	Sep. 06, 2014
Maturity date range, end	Sep. 06, 2016
Capital Lease Obligations, Long-Term [Member]
Long-term debt:
Long-term debt, Weighted Average Interest Rate	4.14%	4.08%
Maturity date range, start	Apr. 01, 2013
Maturity date range, end	Dec. 28, 2018