Benefit Plans (Reconciliation of Level 3 Plan Assets) (Details) (Fair Value, Inputs, Level 3 [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Corporate and other bonds [Member]
Fair value of plan assets at January 1	$ 10
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements		10
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	10	10
Residential Mortgage Backed Securities [Member]
Fair value of plan assets at January 1		52
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period		6
Defined Benefit Plan, Purchases, Sales, and Settlements		(58)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31
Commercial Mortgage Backed Securities [Member]
Fair value of plan assets at January 1	9
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements	(9)	9
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31		9
Other asset-backed [Member]
Fair value of plan assets at January 1	1	5
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements	(1)	(4)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31		1
Total asset-backed [Member]
Fair value of plan assets at January 1	10	57
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period		6
Defined Benefit Plan, Purchases, Sales, and Settlements	(10)	(53)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31		10
Fixed Maturities [Member]
Fair value of plan assets at January 1	20	57
Defined Benefit Plan, Actual Return on Plan Assets Still Held
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period		6
Defined Benefit Plan, Purchases, Sales, and Settlements	(10)	(43)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	10	20
Equity securities [Member]
Fair value of plan assets at January 1	6	5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	(1)	1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	5	6
Hedge Funds [Member]
Fair value of plan assets at January 1	394	339
Defined Benefit Plan, Actual Return on Plan Assets Still Held	5	64
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	5
Defined Benefit Plan, Purchases, Sales, and Settlements	(74)	(9)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	330	394
Private Equity Funds [Member]
Fair value of plan assets at January 1	59	57
Defined Benefit Plan, Actual Return on Plan Assets Still Held	9	6
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements	(3)	(4)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	65	59
Total limited partnerships [Member]
Fair value of plan assets at January 1	453	396
Defined Benefit Plan, Actual Return on Plan Assets Still Held	14	70
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	5
Defined Benefit Plan, Purchases, Sales, and Settlements	(77)	(13)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	395	453
Investment Contracts with Insurance Company [Member]
Fair value of plan assets at January 1	9	9
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period
Defined Benefit Plan, Purchases, Sales, and Settlements
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	10	9
Total assets [Member]
Fair value of plan assets at January 1	488	467
Defined Benefit Plan, Actual Return on Plan Assets Still Held	14	71
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	5	6
Defined Benefit Plan, Purchases, Sales, and Settlements	(87)	(56)
Defined Benefit Plan, Transfers Between Measurement Levels
Fair value of plan assets at December 31	$ 420	$ 488