Supplementary Information - Condensed Consolidating Financial Information (Condensed Consolidating Statement Of Comprehensive Income) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Net income	$ 1.9	$ 68.1	[1]	$ 105.7	[2]	$ 129.0	[3]
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0.6	5.2	[1]	9.9	[2]	15.6	[3]
Net unrealized (losses) gains on cash flow hedges	0.7	(5.5)	[1]	(0.6)		(10.5)	[3]
Total other comprehensive income (loss)	1.3	(0.6)	[1]	9.3	[2]	5.1	[3]
Total comprehensive income	3.2	67.5	[1]	115.0	[2]	134.1	[3]
Total comprehensive income (loss)attributable to noncontrolling interests	(0.6)	0.4	[1]	(2.0)	[2]	(12.8)	[3]
Total comprehensive income attributable to partners	2.6	67.9	[1]	113.0	[2]	121.3	[3]
Predecessor Equity [Member]
Other comprehensive income (loss):
Net unrealized (losses) gains on cash flow hedges		(0.3)		(0.6)		(0.7)
Net unrealized losses on cash flow hedges - predecessor		(0.3)	[1]	(0.6)	[2]	(0.7)	[3]
Total comprehensive income				2.0		13.6
DCP Midstream Partners, LP [Member]
Net income	1.3	68.5	[1]	103.7	[2]	116.2	[3]
Other comprehensive income (loss):
Other comprehensive income (loss) from consolidated subsidiaries	1.3			9.3	[2]	5.1	[3]
Other comprehensive income (loss) from consolidated subsidiaries		(0.6)	[1]
Total other comprehensive income (loss)	1.3	(0.6)	[1]	9.3	[2]	5.1	[3]
Total comprehensive income	2.6	67.9	[1]	113.0	[2]	121.3	[3]
Total comprehensive income attributable to partners	2.6	67.9	[1]	113.0	[2]	121.3	[3]
Subsidiary Issuer [Member]
Net income	1.3	68.5	[1]	103.7	[2]	116.2	[3]
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings	0.6	5.1	[1]	9.9	[2]	15.4	[3]
Net unrealized (losses) gains on cash flow hedges	(0.4)	(5.3)	[1]	(0.6)	[2]	(9.5)	[3]
Other comprehensive income (loss) from consolidated subsidiaries	1.1					(0.8)	[3]
Other comprehensive income (loss) from consolidated subsidiaries		(0.4)	[1]
Total other comprehensive income (loss)	1.3	(0.6)	[1]	9.3	[2]	5.1	[3]
Total comprehensive income	2.6	67.9	[1]	113.0	[2]	121.3	[3]
Total comprehensive income attributable to partners	2.6	67.9	[1]	113.0	[2]	121.3	[3]
Non-Guarantor Subsidiaries [Member]
Net income	10.5	76.4	[1]	137.2	[2]	153.7	[3]
Other comprehensive income (loss):
Reclassification of cash flow hedge losses into earnings		0.1	[1]			0.2	[3]
Net unrealized (losses) gains on cash flow hedges	1.1	(0.2)	[1]	0.6	[2]	(0.3)	[3]
Total other comprehensive income (loss)	1.1	(0.4)	[1]			(0.8)	[3]
Total comprehensive income	11.6	76.0	[1]	137.2	[2]	152.9	[3]
Total comprehensive income (loss)attributable to noncontrolling interests	(0.6)	0.4	[1]	(2.0)	[2]	(12.8)	[3]
Total comprehensive income attributable to partners	11.0	76.4	[1]	135.2	[2]	140.1	[3]
Non-Guarantor Subsidiaries [Member] | Predecessor Equity [Member]
Other comprehensive income (loss):
Net unrealized losses on cash flow hedges - predecessor		(0.3)	[1]	(0.6)	[2]	(0.7)	[3]
Consolidating Adjustments [Member]
Net income	(11.2)	(145.3)	[1]	(238.9)	[2]	(257.1)	[3]
Other comprehensive income (loss):
Other comprehensive income (loss) from consolidated subsidiaries	(2.4)			(9.3)	[2]	(4.3)	[3]
Other comprehensive income (loss) from consolidated subsidiaries		1.0	[1]
Total other comprehensive income (loss)	(2.4)	1.0	[1]	(9.3)	[2]	(4.3)	[3]
Total comprehensive income	(13.6)	(144.3)	[1]	(248.2)	[2]	(261.4)	[3]
Total comprehensive income attributable to partners	$ (13.6)	$ (144.3)	[1]	$ (248.2)	[2]	$ (261.4)	[3]

[1] The financial information for the three months ended September 30, 2011 includes the results of Southeast Texas, a transfer of net assets between entities under common control that was accounted for as if the transfer occurred at the beginning of the period, and prior years are retrospectively adjusted to furnish comparative information similar to the pooling method.

[2] The financial information for the nine months ended September 30, 2012 includes the results of Southeast Texas, a transfer of net assets between entities under common control that was accounted for as if the transfer occurred at the beginning of the period, and prior years are retrospectively adjusted to furnish comparative information similar to the pooling method.

[3] The financial information for the nine months ended September 30, 2011 includes the results of Southeast Texas, a transfer of net assets between entities under common control that was accounted for as if the transfer occurred at the beginning of the period, and prior years are retrospectively adjusted to furnish comparative information similar to the pooling method.