Discontinued Operations (Schedule Of Cash Collateral Offset Against Derivative Positions) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012
Derivative [Line Items]
Cash collateral pledged to counterparties with the right to reclaim	$ 2	[1]	$ 6	[1]
Discontinued Operations [Member]
Derivative [Line Items]
Cash collateral pledged to counterparties with the right to reclaim	$ 8	[1]	$ 12	[1]

[1] Includes cash deposits on commodity brokerage accounts.