Equity-based Awards (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended				3 Months Ended		9 Months Ended				8 Months Ended		3 Months Ended			9 Months Ended					9 Months Ended	3 Months Ended				9 Months Ended				3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 Long-Term Incentive Plan (1998) [Member]	Sep. 30, 2011 Long-Term Incentive Plan (2008) [Member]	Sep. 30, 2011 Restricted Common Unit Awards [Member]	Sep. 30, 2010 Restricted Common Unit Awards [Member]	Sep. 30, 2011 Restricted Common Unit Awards [Member]	Sep. 30, 2010 Restricted Common Unit Awards [Member]	Sep. 30, 2011 Restricted Common Unit Awards [Member] Enterprise [Member]		Sep. 06, 2011 Restricted Common Unit Awards [Member] Duncan Energy Partners [Member]		Sep. 30, 2011 Unit Option Awards [Member]		Sep. 30, 2010 Unit Option Awards [Member]	Sep. 30, 2011 Unit Option Awards [Member]		Sep. 30, 2010 Unit Option Awards [Member]	Dec. 31, 2010 Unit Option Awards [Member]		Sep. 30, 2011 Unit Option Awards [Member] Enterprise [Member]	Sep. 30, 2011 Other Equity-based Awards [Member]		Sep. 30, 2010 Other Equity-based Awards [Member]		Sep. 30, 2011 Other Equity-based Awards [Member]		Sep. 30, 2010 Other Equity-based Awards [Member]		Sep. 30, 2010 Unit Appreciation Rights [Member]	Sep. 30, 2011 Unit Appreciation Rights [Member]	Sep. 30, 2010 Unit Appreciation Rights [Member]	Dec. 31, 2010 Unit Appreciation Rights [Member]	Sep. 30, 2010 Employee Partnerships [Member]	Sep. 30, 2010 Employee Partnerships [Member]
Equity-based compensation expense [Abstract]
Total compensation expense	$ 12.8	$ 38.5	$ 37.8	$ 58.3			$ 11.9	$ 9.6	$ 35.4	$ 23.3					$ 0.7		$ 1.0	$ 2.4		$ 2.4				$ 0.2	[1]	$ 27.9	[1]	$ 0	[1]	$ 32.6	[1]	$ 0.2	$ (0.6)	$ 0.5		$ 27.5	$ 31.3
Maximum number of common units that may be issued as awards (in units)					7,000,000	10,000,000
Remaining number of common units available to be issued as awards (in units)					1,488,906	4,737,750
Summary of awards activity, equity instruments other than options [Roll Forward]
Beginning of period (in units)											3,561,614		0																				170,104
Granted (in units)											1,381,530	[2]	3,666	[3]
Vested (in units)											(886,508)		(3,666)	[3]																			(17,776)
Forfeited (in units)											(129,899)
Settled or forfeited (in units)																																	(45,000)
End of period (in units)											3,926,737		0																				107,328
Accrued liability for UARs																																	0.4		1.0
Summary of awards activity, equity instruments other than options, additional disclosures [Abstract]
Weighted-average grant date fair value per unit, at beginning of period (in dollars per unit)											$ 29.78	[4]	$ 0	[4]
Granted weighted-average grant date fair value per unit (in dollars per unit)											$ 43.63	[2],[4]	$ 32.56	[3],[4]
Vested weighted-average grant date fair value per unit (in dollars per unit)											$ 31.46	[4]	$ 32.56	[3],[4]
Forfeited weighted-average grant date fair value per unit (in dollars per unit)											$ 33.51	[4]
Weighted-average grant date fair value per unit, at end of period (in dollars per unit)											$ 34.15	[4]	$ 0	[4]																			$ 37.00
Aggregate grant date fair value											60.3		0.1
Minimum grant date market price of common units (in dollars per unit)											$ 40.54
Maximum grant date market price of common units (in dollars per unit)											$ 43.70
Grant date market price of common units (in dollars per unit)													$ 32.56
Estimated forfeiture rate (in hundredths)											4.60%
Cash distributions paid to restricted common unit holders							2.4	2.0	7.2	5.8
Total intrinsic value of restricted common unit awards vesting during period							2.3	0.6	37.5	12.0
Summary of awards activity, options [Roll Forward]
Number of Units (in units)															3,753,420			3,753,420			3,753,420
Summary of awards activity, options, additional disclosures [Abstract]
Weighted average strike price (in dollars per unit)															$ 28.08			$ 28.08			$ 28.08
Weighted average remaining contractual term (in years)															2.9			2.9			3.6
Aggregate intrinsic value															6.7	[5]		6.7	[5]		0	[5]
Exercisable (in units)															0	[6]		0	[6]
Exercisable - Weighted average remaining contractual term (in years)															0	[6]		0	[6]
Exercisable - Aggregate intrinsic value															0	[5],[6]		0	[5],[6]
Option awards vested during period (in units)																		712,280
Awards vest during 2012 (in units)															736,000			736,000
Awards vest during 2013 (in units)															1,520,140			1,520,140
Awards vest during 2014 (in units)															785,000			785,000
Total intrinsic value of unit option awards exercised during period																	7.5			9.7
Cash received from EPCO in connection with the exercise of unit option awards																	5.0			6.6
Unit option-related reimbursements to EPCO																	7.5			9.7
Equity-based awards, additional disclosures [Abstract]
Unrecognized compensation cost							$ 61.3		$ 61.3		$ 57.9				$ 4.4			$ 4.4					$ 3.9
Recognition period for total unrecognized compensation cost (in years)											1.9												1.7

[1] Primarily consists of unit appreciation rights ("UARs"), phantom units and similar awards. Also, the amounts presented for 2010 include awards related to limited partnership interests in the Employee Partnerships, which were liquidated in August 2010.

[2] The aggregate grant date fair value of restricted common unit awards issued in 2011 was $60.3 million based on a grant date market price of our common units ranging from $40.54 to $43.70 per unit. An estimated annual forfeiture rate of 4.6% was applied to these awards.

[3] The aggregate grant date fair value of restricted common unit awards issued in 2011 was $0.1 million based on a grant date market price of Duncan Energy Partners' common units of $32.56 per unit. These awards vested upon issuance.

[4] Determined by dividing the aggregate grant date fair value of awards (before an allowance for forfeitures) by the number of awards issued.

[5] Aggregate intrinsic value reflects fully vested unit options at the date indicated. There were no vested unit options outstanding at December 31, 2010.

[6] We were committed to issue 3,753,420 of our common units at September 30, 2011 if all outstanding options awarded were exercised. Option awards outstanding at September 30, 2011 include 712,280 awards that vested during the first nine months of 2011. Of the remaining outstanding option awards at September 30, 2011, 736,000, 1,520,140 and 785,000 will vest in 2012, 2013, and 2014, respectively. These unit option awards become exercisable in the calendar year following the year in which they vest.