Pension and Other Postemployment Benefits (Details 4) (Pensions, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Actual return on plan assets:
Ending balance	$ 6,707	$ 5,883
Private equity funds
Actual return on plan assets:
Ending balance	33	135
Real estate funds
Actual return on plan assets:
Ending balance	357	327
Derivatives
Actual return on plan assets:
Ending balance	18	145
Level 3
Actual return on plan assets:
Ending balance	390	532
Level 3 | Private equity funds
Reconciliation of changes in the fair value of pension investments
Beginning balance	135	119
Actual return on plan assets:
Unrealized gains (losses)	(14)	11
Realized gains (losses)	(10)	5
Purchases, sales and settlements	0	0
Transfers in (out)	(78)	0
Ending balance	33	135
Level 3 | Real estate funds
Reconciliation of changes in the fair value of pension investments
Beginning balance	327	282
Actual return on plan assets:
Unrealized gains (losses)	29	28
Realized gains (losses)	4	17
Purchases, sales and settlements	0	0
Transfers in (out)	(3)	0
Ending balance	357	327
Level 3 | Derivatives
Reconciliation of changes in the fair value of pension investments
Beginning balance	70	0
Actual return on plan assets:
Unrealized gains (losses)	0	7
Realized gains (losses)	0	0
Purchases, sales and settlements	(70)	63
Transfers in (out)	0	0
Ending balance	$ 0	$ 70