Equity and Distributions, Noncontrolling Interests (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Components of noncontrolling interests [Abstract]
Joint venture partners	$ 225.6	$ 108.3
Components of net income attributable to noncontrolling interests [Abstract]
Limited partners of Duncan Energy Partners other than EPO and its subsidiaries (prior to Duncan Merger)	0	0	20.9
Joint venture partners	10.2	8.1	20.5
Total	10.2	8.1	41.4
Cash distributions paid to noncontrolling interests:
Limited partners of Duncan Energy Partners other than EPO and its subsidiaries (prior to Duncan Merger)	0	0	32.9
Joint venture partners	8.9	13.3	27.8
Total	8.9	13.3	60.7
Cash contributions from noncontrolling interests:
Limited partners of Duncan Energy Partners other than EPO and its subsidiaries (prior to Duncan Merger)	0	0	2.6
Joint venture partners	115.4	6.6	5.9
Total	$ 115.4	$ 6.6	$ 8.5