Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash paid for interest, net of amounts capitalized	$ 7.0	$ 7.4
Cash paid for income taxes, net of income tax refunds	0.8	29.9
Property, plant and equipment acquired with accounts payable	8.3	11.6
Other non-cash additions of property, plant and equipment	5.8	1.6
Non-cash change in parent advances		4.4
Non-cash distributions to DCP Midstream, LLC		2.6
Non-cash contributions from DCP Midstream, LLC	3.3
Non-cash excess purchase price over acquired assets	$ 60.0