Risk Management, Derivative Instruments And Hedging Activities (Information Regarding Cash Collateral Under Master Netting Arrangements) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Risk Management, Derivative Instruments And Hedging Activities [Abstract]
Amounts offset against derivative positions on the Consolidated Balance Sheets, Receivables	$ 10		$ 2
Amounts not offset against net derivative positions on the Consolidated Balance Sheets, Receivables	30	[1]	2	[1]
Amounts not offset against net derivative positions on the Consolidated Balance Sheets, Payables			$ 3	[1]

[1] Amounts primarily represent margin deposits related to futures contracts.