Benefit Plans (Estimated Future Minimum Benefit Payments to Participants) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	$ 176
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	181
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	184
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	188
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	191
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	1,002
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan, Expected Future Benefit Payments in Year One	6
Defined Benefit Plan, Expected Future Benefit Payments in Year Two	6
Defined Benefit Plan, Expected Future Benefit Payments in Year Three	5
Defined Benefit Plan, Expected Future Benefit Payments in Year Four	5
Defined Benefit Plan, Expected Future Benefit Payments in Year Five	5
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	$ 18