PARTNERS' CAPITAL (Schedule of Changes in Partners' Capital) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Beginning balance			$ 5,120.4
Net income	$ (97.1)	$ 43.9	43.0	$ 137.2
Accretion of discount on preferred units	4.1	3.7	8.0	7.3
Ending balance	5,418.5		5,418.5
Noncontrolling interest:
Noncontrolling interest, beginning balance			3,609.0	1,975.6
Capital contributions			502.6	$ 612.9
Acquisition of noncontrolling interest in subsidiary			(403.7)
Other comprehensive loss allocated to noncontrolling interest	(1.9)	(0.3)	(2.6)	$ (0.3)
Net income	10.0	42.4	61.3	78.7
Distributions to noncontrolling interest			(171.2)	(42.5)
Noncontrolling interest, ending balance	3,595.4	2,624.4	3,595.4	2,624.4
Total partners' capital	9,013.9	7,998.0	9,013.9	7,998.0	$ 8,729.4
Series 1 Preferred Interests [Member]
Beginning balance			1,175.6	1,160.7
Net income			45.0	45.0
Distributions			(45.0)	(45.0)
Accretion of discount on preferred units			8.0	7.3
Ending balance	1,183.6	1,168.0	1,183.6	1,168.0
General and Limited Partner Interests [Member]
Beginning balance			4,156.2	$ 4,637.7
Proceeds from issuance of partnership interests, net of costs			294.8
Net income			43.0	$ 137.2
Distributions			(403.8)	$ (356.9)
Acquisition of noncontrolling interest in subsidiary			403.7
Ending balance	4,493.9	4,418.0	4,493.9	$ 4,418.0
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance			(211.4)	(76.6)
Changes in fair value of derivative financial instruments reclassified to earnings			(3.5)	16.6
Changes in fair value of derivative financial instruments recognized in other comprehensive loss			(44.1)	(152.4)
Ending balance	$ (259.0)	$ (212.4)	$ (259.0)	$ (212.4)