Benefit Plans (Pension Plan Assets Measured At Fair Value On A Recurring Basis) (Details) (Pension Benefits [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,435	$ 2,468	$ 2,303
Corporate And Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	387	315
States, Municipalities And Political Subdivisions [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104	92
Asset-Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	276	240
Total Fixed Maturity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	767	647
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	466	535
Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	112	121
Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98	84
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	877	980
Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84	76
Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	961	1,056
Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21	16
Investment Contracts With Insurance Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	9
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	561	651
Level 1 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	386	452
Level 1 [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77	114
Level 1 [Member] | Fixed Income Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	98	84
Level 1 [Member] | Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,421	1,289
Level 2 [Member] | Corporate And Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	377	305
Level 2 [Member] | States, Municipalities And Political Subdivisions [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	104	92
Level 2 [Member] | Asset-Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	276	230
Level 2 [Member] | Total Fixed Maturity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	757	627
Level 2 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	75	77
Level 2 [Member] | Short Term Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35	7
Level 2 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	533	563
Level 2 [Member] | Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	533	563
Level 2 [Member] | Other Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	21	15
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	453	528
Level 3 [Member] | Corporate And Other Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	10
Level 3 [Member] | Asset-Backed Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		10
Level 3 [Member] | Total Fixed Maturity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	20
Level 3 [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	6
Level 3 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	344	417
Level 3 [Member] | Private Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	84	76
Level 3 [Member] | Limited Partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	428	493
Level 3 [Member] | Investment Contracts With Insurance Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 10	$ 9