XML 106 R53.htm IDEA: XBRL DOCUMENT v2.4.0.6
Organization (Details) (USD $)
3 Months Ended 12 Months Ended
Dec. 31, 2011
Sep. 30, 2011
Jun. 30, 2011
Mar. 31, 2011
Dec. 31, 2010
Sep. 30, 2010
Jun. 30, 2010
Mar. 31, 2010
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Organization [Line Items]                      
Operating income $ 91,000,000 $ 195,000,000 $ 202,000,000 $ 149,000,000 $ 88,000,000 $ 212,000,000 $ 193,000,000 $ 131,000,000 $ 637,000,000 $ 624,000,000 $ 648,000,000
Proceeds from sale of power generation business                   1,640,000,000  
Subsidiary of Common Parent [Member] | Retail Energy Service Business [Member]
                     
Organization [Line Items]                      
Operating revenue                 900,000,000 1,600,000,000 2,300,000,000
Operating income                 11,000,000 59,000,000 88,000,000
Letters of credit 1,000,000               1,000,000    
Posted cash collateral $ 112,000,000               $ 112,000,000