Pension and Other Postretirement Benefits (Details 4) (Pensions, USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Actual return on plan assets:
Ending balance	$ 5,883,000,000	$ 4,521,000,000
Private equity funds
Actual return on plan assets:
Ending balance	135,000,000	119,000,000
Real estate funds
Actual return on plan assets:
Ending balance	327,000,000	284,000,000
Derivatives
Actual return on plan assets:
Ending balance	145,000,000
Level 3
Actual return on plan assets:
Ending balance	532,000,000	401,000,000
Level 3 | Private equity funds
Reconciliation of changes in the fair value of pension investments
Beginning balance	119,000,000	137,000,000
Actual return on plan assets:
Unrealized gains (losses)	11,000,000	1,000,000
Realized gains (losses)	5,000,000	11,000,000
Purchases, sales and settlements	0	(28,000,000)
Transfers in (out)	0	(2,000,000)
Ending balance	135,000,000	119,000,000
Level 3 | Real estate funds
Reconciliation of changes in the fair value of pension investments
Beginning balance	282,000,000	241,000,000
Actual return on plan assets:
Unrealized gains (losses)	28,000,000	45,000,000
Realized gains (losses)	17,000,000	(3,000,000)
Purchases, sales and settlements	0	(1,000,000)
Transfers in (out)	0	0
Ending balance	327,000,000	282,000,000
Level 3 | Derivatives
Reconciliation of changes in the fair value of pension investments
Beginning balance	0	0
Actual return on plan assets:
Unrealized gains (losses)	7,000,000	0
Realized gains (losses)	0	0
Purchases, sales and settlements	63,000,000	0
Transfers in (out)	0	0
Ending balance	$ 70,000,000	$ 0