DEBT - Schedule of Debt (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Short-term debt and current portion of long-term debt:
Short-term debt, weighted-average interest rate	1.70%	1.79%
Short-term debt	$ 44,107,000	$ 35,509,000
Current portion of long-term debt	696,441,000	790,560,000
Total short-term debt and current portion of long-term debt	740,548,000	826,069,000
Long-term debt:
U.S. commercial paper	567,000,000
Total before fair market value adjustment	5,967,329,000	5,394,787,000
Fair market value adjustment on notes subject to hedging	(15,986,000)	(7,192,000)
Debt issuance costs	(17,525,000)	(13,453,000)
Total after fair market value adjustment	5,933,818,000	5,374,142,000
Current portion of long-term debt	(696,441,000)	(790,560,000)
Long-term debt	5,237,377,000	4,583,582,000
Total debt	5,977,925,000	5,409,651,000
Unamortized original issue discounts	8,000,000	6,000,000
Aggregate notional amount of interest rate swaps	$ 825,000,000	$ 825,000,000
U.S. commercial paper
Long-term debt:
Long-term debt, weighted-average interest rate	2.28%	1.56%
U.S. commercial paper	$ 519,916,000	$ 570,218,000
Canadian commercial paper
Long-term debt:
Long-term debt, weighted-average interest rate	1.70%	0.00%
U.S. commercial paper	$ 47,175,000	$ 0
Global revolving credit facility
Long-term debt:
Long-term debt, weighted-average interest rate	3.12%	2.80%
Global revolving credit facility	$ 600,000	$ 17,328,000
Unsecured U.S. notes — Medium-term notes
Long-term debt:
Long-term debt, weighted-average interest rate	3.06%	2.73%
Unsecured U.S. notes - Medium-term notes	$ 4,562,972,000	$ 4,014,091,000
Unsecured U.S. obligations
Long-term debt:
Long-term debt, weighted-average interest rate	3.34%	2.79%
Unsecured U.S. obligations	$ 50,000,000	$ 50,000,000
Unsecured foreign obligations
Long-term debt:
Long-term debt, weighted-average interest rate	1.61%	1.50%
Obligations	$ 224,406,000	$ 230,380,000
Asset-backed U.S. obligations
Long-term debt:
Long-term debt, weighted-average interest rate	2.12%	1.85%
Obligations	$ 544,911,000	$ 491,899,000
Capital lease obligations
Long-term debt:
Long-term debt, weighted-average interest rate	3.48%	3.53%
Capital lease obligations	$ 17,349,000	$ 20,871,000

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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