VARIABLE INTEREST ENTITIES (VIE Assets and Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 108.8	$ 148.1	$ 197.9	$ 164.8
Restricted cash	24.5	37.6
Receivables, trade and other, net	14.5	25.2
Due from General Partner and affiliates	90.6	59.4
Accrued receivables	39.7	77.9
Inventory	30.9	35.1
Other current assets	92.2	173.0
Property, plant and equipment, net	16,722.6	17,412.4
Equity investment in joint ventures	360.7	372.3
Intangible assets, net	258.5	280.0
Other assets, net	160.3	153.3
LIABILITIES
Accounts payable and other	409.6	654.9
Due to General Partner and affiliates	213.9	190.9
Accrued purchases	176.8	146.1
Interest payable	95.1	98.9
Environmental liabilities	99.9	95.8	$ 6.3
Property and other taxes payable	106.9	103.7
Long-term debt	7,884.4	7,728.4
Other long-term liabilities	222.7	305.2
Variable Interest Entity, Primary Beneficiary [Member]
ASSETS
Cash and cash equivalents	44.7	108.7
Restricted cash	11.0	20.6
Receivables, trade and other, net	10.3	22.8
Due from General Partner and affiliates	76.1	51.9
Accrued receivables	38.1	77.4
Inventory	29.6	35.1
Other current assets	91.3	165.3
Property, plant and equipment, net	16,267.8	16,766.6
Equity investment in joint ventures	360.7	372.3
Intangible assets, net	258.4	279.8
Other assets, net	157.6	147.9
LIABILITIES
Accounts payable and other	236.3	534.2
Due to General Partner and affiliates	129.0	123.4
Accrued purchases	176.4	144.1
Interest payable	8.5	8.7
Environmental liabilities	99.8	95.7
Property and other taxes payable	103.8	100.5
Long-term debt	1,017.8	1,087.4
Other long-term liabilities	$ 179.3	$ 209.7