Investments - Appreciation (Depreciation) on Fixed Maturities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 14,289	$ 15,465
Unrealized Appreciation	1,435	2,254
Unrealized (Depreciation)	(85)	(30)
Total fair value	15,639	17,689
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	535	883
Unrealized (Depreciation)	(18)	(8)
Total fair value	2,700	3,100
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	443	509
Unrealized Appreciation	282	393
Unrealized (Depreciation)	(1)	0
Total fair value	724	902
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,018	2,169
Unrealized Appreciation	183	270
Unrealized (Depreciation)	(5)	(2)
Total fair value	2,196	2,437
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,116	1,197
Unrealized Appreciation	70	126
Unrealized (Depreciation)	(9)	(1)
Total fair value	1,177	1,322
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,763	10,590
Unrealized Appreciation	802	1,308
Unrealized (Depreciation)	(63)	(17)
Total fair value	10,502	11,881
Federal agency mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83	121
Unrealized Appreciation	0	1
Unrealized (Depreciation)	0	0
Total fair value	83	122
Other mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67	82
Unrealized Appreciation	4	11
Unrealized (Depreciation)	(4)	(4)
Total fair value	67	89
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	799	797
Unrealized Appreciation	94	145
Unrealized (Depreciation)	(3)	(6)
Total fair value	$ 890	$ 936