v2.4.0.6
Schedule of Valuation and Qualifying Accounts Disclosure (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
      
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at Beginning of Year $ 13 $ 2 $ 14
Charged to Expense (1) 7 (12)
Deductions (5) [1] 0 [1] 0 [1]
Charged to Other Accounts (1) 4 0
Balance at End of Year 6 13 2
Deferred Tax Asset Valuation Allowance [Member]
      
Movement in Valuation Allowances and Reserves [Roll Forward]      
Balance at Beginning of Year 2,336 2,386 2,572
Charged to Expense (114) (50) (186)
Deductions 0 [1] 0 [1] 0 [1]
Charged to Other Accounts 0 0 0
Balance at End of Year $ 2,222 $ 2,336 $ 2,386
[1] Represents write-offs of accounts considered to be uncollectible and previously reserved.