Agreements And Transactions With Affiliates (Balances With Affiliates) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Related Party Transaction [Line Items]
Accounts receivable	$ 67.8		$ 106.2
Accounts payable	14.1		46.8
DCP Midstream, LLC [Member]
Related Party Transaction [Line Items]
Accounts receivable	67.4		100.0
Accounts payable	14.1		22.6
Unrealized gains on derivative instruments - current	44.8		0.6
Unrealized gains on derivative instruments - long-term	30.9
Unrealized losses on derivative instruments - current	(21.5)		(0.6)
Unrealized losses on derivative instruments - long-term	(1.1)
Spectra Energy [Member]
Related Party Transaction [Line Items]
Accounts receivable	0.3		0.1
Accounts payable			21.4
Conoco Phillips [Member]
Related Party Transaction [Line Items]
Accounts receivable			6.1	[1]
Accounts payable			0.4	[1]
Unrealized gains on derivative instruments - current			2.5	[1]
Unrealized losses on derivative instruments - current			(2.0)	[1]
Phillips 66 [Member]
Related Party Transaction [Line Items]
Accounts receivable	0.1	[1]
Unconsolidated Affiliates [Member]
Related Party Transaction [Line Items]
Accounts payable			$ 2.4

[1] In connection with the Phillips 66 separation, ConocoPhillips is not considered to be a related party for periods after April 30, 2012 and Phillips 66 is considered a related party for periods starting May 1, 2012.