Use of Collateral (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Use of Collateral [Abstract]
Margin Deposit Assets	$ 261	[1]	$ 196	[1]
Natural gas and power prepayments	28		35
Total margin deposits and natural gas and power prepayments with our counterparties	289	[2]	231	[2]
Letters of credit issued	488		484
First priority liens under power and natural gas agreements	31		14
First priority liens under interest rate swap agreements	132		206
Total letters of credit and first priority liens with our counterparties	651		704
Security Deposit Liability	5	[1],[3]	11	[1],[3]
Letters of credit posted with us by our counterparties	2		1
Total margin deposits and letters of credit posted with us by our counterparties	7		12
Use of Collateral (Textuals) [Abstract]
Margin And Prepayment Amounts Included In Other Assets	17		20
Margin And Prepayment Amounts Included In Margin Deposits And Other Prepaid Expenses	$ 272		$ 211

[1] Balances are subject to master netting arrangements and presented on a gross basis on our Consolidated Balance Sheets. We do not offset fair value amounts recognized for derivative instruments executed with the same counterparty under a master netting arrangement for financial statement presentation, and we do not offset amounts recognized for the right to reclaim, or the obligation to return, cash collateral with corresponding derivative instrument fair values. See Note 8 for further discussion of our derivative instruments subject to master netting arrangements.

[2] At December 31, 2013 and 2012, $272 million and $211 million, respectively, were included in margin deposits and other prepaid expense and $17 million and $20 million, respectively, were included in other assets on our Consolidated Balance Sheets.

[3] Included in other current liabilities on our Consolidated Balance Sheets.