PARTNERS' CAPITAL (Schedule of Changes in Partners' Capital) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Beginning balance	$ 4,967.6
Net income	22.5	$ 22.5
Accretion of discount on preferred units	1.1	3.9
Ending balance	4,755.1
Noncontrolling interest
Beginning balance	3,944.5	3,609.0
Capital contributions	54.4	199.5
Acquisition of noncontrolling interest in subsidiary	0.0	(403.7)
Other comprehensive loss allocated to noncontrolling interest	0.0	(0.7)
Distributions to noncontrolling interest	(7.6)	(107.0)
Net income	68.8	51.3
Ending balance	4,060.1	3,348.4
Total partners’ capital at end of period	8,815.2	8,971.0
Series 1 Preferred interests [Member]
Beginning balance	1,186.8	1,175.6
Net income	22.5	22.5
Accretion of discount on preferred units	1.1	3.9
Distributions	(22.5)	(22.5)
Ending balance	1,187.9	1,179.5
General and limited partner interests [Member]
Beginning balance	4,150.8	4,156.2
Net income	80.0	140.1
Proceeds from issuance of partnership interests, net of costs	0.0	294.8
Distributions	(216.0)	(194.2)
Acquisition of noncontrolling interest in subsidiary	0.0	403.7
Ending balance	4,014.8	4,800.6
Accumulated other comprehensive loss [Member]
Beginning balance	(370.0)	(211.4)
Changes in fair value of derivative financial instruments reclassified to earnings	10.0	(1.0)
Changes in fair value of derivative financial instruments recognized in other comprehensive loss	(87.6)	(145.1)
Ending balance	$ (447.6)	$ (357.5)