Benefit Plans (Reconciliation of Level 3 Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	$ 478	$ 520
Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	793	841
Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	507	605
Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	865	969
Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	113	114
Total limited partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	978	1,083
Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at December 31	2,456	2,656
Fair Value, Inputs, Level 3 [Member] | Corporate and other bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	15	11
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	(1)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	5
Defined Benefit Plan, Net transfers into (out of) Level 3	0	0
Fair value of plan assets at December 31	15	15
Fair Value, Inputs, Level 3 [Member] | Fixed Maturities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	15	11
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	(1)
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	0	5
Defined Benefit Plan, Net transfers into (out of) Level 3	0	0
Fair value of plan assets at December 31	15	15
Fair Value, Inputs, Level 3 [Member] | Equity securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	8	5
Defined Benefit Plan, Actual Return on Plan Assets Still Held	0	3
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	(8)	0
Defined Benefit Plan, Net transfers into (out of) Level 3	0	0
Fair value of plan assets at December 31	0	8
Fair Value, Inputs, Level 3 [Member] | Hedge Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	322	359
Defined Benefit Plan, Actual Return on Plan Assets Still Held	19	56
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	(38)	(77)
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(16)
Fair value of plan assets at December 31	303	322
Fair Value, Inputs, Level 3 [Member] | Private Equity Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	114	62
Defined Benefit Plan, Actual Return on Plan Assets Still Held	19	0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	(20)	52
Defined Benefit Plan, Net transfers into (out of) Level 3	0	0
Fair value of plan assets at December 31	113	114
Fair Value, Inputs, Level 3 [Member] | Total limited partnerships [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	436	421
Defined Benefit Plan, Actual Return on Plan Assets Still Held	38	56
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	(58)	(25)
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(16)
Fair value of plan assets at December 31	416	436
Fair Value, Inputs, Level 3 [Member] | Investment Contracts with Insurance Company [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1		10
Defined Benefit Plan, Actual Return on Plan Assets Still Held		0
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period		0
Defined Benefit Plan, Purchases, Sales, and Settlements		(10)
Defined Benefit Plan, Net transfers into (out of) Level 3		0
Fair value of plan assets at December 31		0
Fair Value, Inputs, Level 3 [Member] | Total assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at January 1	459	447
Defined Benefit Plan, Actual Return on Plan Assets Still Held	38	58
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0	0
Defined Benefit Plan, Purchases, Sales, and Settlements	(66)	(30)
Defined Benefit Plan, Net transfers into (out of) Level 3	0	(16)
Fair value of plan assets at December 31	$ 431	$ 459