Employee Benefit Plans (Schedule of Estimated Future Employer Contributions) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Pension Plans, Defined Benefit [Member] | Qualified Plans [Member]
2012	$ 55
2013	59
2014	63
2015	67
2016	72
2017-2021	436
Pension Plans, Defined Benefit [Member] | Non Qualified Plans [Member]
2012	9
2013	10
2014	11
2015	12
2016	13
2017-2021	70
Other Postretirement Benefit Plans, Defined Benefit [Member]
2012	7	[1]
2013	7	[1]
2014	7	[1]
2015	7	[1]
2016	7	[1]
2017-2021	$ 29	[1]

[1] Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies.