Employee Benefits (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Pension Benefits [Member]
Changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]
Net actuarial loss (gain)	$ 355	$ 16	$ (83)
Amortization of net actuarial loss and prior service cost and other	(68)	(64)	(46)
Total Changes in plan assets and benefit obligations recognized in other comprehensive income	287	(48)	(129)
Other Postretirement Benefits [Member]
Changes in plan assets and benefit obligations recognized in other comprehensive income [Abstract]
Net actuarial loss (gain)	45	30	(4)
Amortization of net actuarial loss and prior service cost and other	(3)	(2)	(1)
Total Changes in plan assets and benefit obligations recognized in other comprehensive income	$ 42	$ 28	$ (5)