Investments - Appreciation (Depreciation) on Fixed Maturities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 16,156	$ 15,267
Unrealized Appreciation	1,545	1,312
Unrealized (Depreciation)	(51)	(99)
Total Fair Value	17,650	16,480
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	613	478
Unrealized (Depreciation)	(8)	(20)
Total Fair Value	2,800	2,600
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	835	640
Unrealized Appreciation	294	242
Unrealized (Depreciation)	(1)	(2)
Total Fair Value	1,128	880
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,922	1,983
Unrealized Appreciation	178	167
Unrealized (Depreciation)	(4)	(6)
Total Fair Value	2,096	2,144
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,517	1,392
Unrealized Appreciation	74	64
Unrealized (Depreciation)	(8)	(12)
Total Fair Value	1,583	1,444
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,962	10,301
Unrealized Appreciation	888	749
Unrealized (Depreciation)	(36)	(74)
Total Fair Value	11,814	10,976
Federal agency mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	71	77
Unrealized Appreciation	0	0
Unrealized (Depreciation)	0	(1)
Total Fair Value	71	76
Other mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	78	76
Unrealized Appreciation	4	3
Unrealized (Depreciation)	(2)	(2)
Total Fair Value	80	77
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	771	798
Unrealized Appreciation	107	87
Unrealized (Depreciation)	0	(2)
Total Fair Value	$ 878	$ 883