Inventories (Schedule Of Inventories) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Total inventories	$ 71.6	$ 87.9	[1]
Natural Gas [Member]
Total inventories	15.7	25.6
Natural Gas Liquids [Member]
Total inventories	$ 55.9	$ 62.3

[1] The financial information as of December 31, 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.