v2.4.0.6
Regulatory Matters Regulatory Matters (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Regulatory Assets [Line Items]    
Regulatory Assets, Current $ 73 $ 62
Assets held for sale 32 298
Regulatory Assets, Noncurrent 393 402
Regulatory Assets 466 464
Regulatory Liability, Current 7 7
Regulatory Liability, Noncurrent 104 113
Regulatory Liabilities $ 111 $ 120