Benefit Obligations (Schedule of Amortization of Accumulated Other Comprehensive Income (Loss), Net Into Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Pension Benefits [Member]
Net actuarial (gain) loss	$ 57
Prior service cost	1
Total	58
Postretirement Benefits [Member]
Net actuarial (gain) loss	(1)
Prior service cost	0
Total	$ (1)