Investments - Appreciation (Depreciation) on Fixed Maturities (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 17,278	$ 15,273
Unrealized Appreciation	1,747	1,312
Unrealized (Depreciation)	(42)	(99)
Total Fair Value	18,983	16,486
Commitments to purchase fixed maturities	74
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	758	478
Unrealized (Depreciation)	(2)	(20)
Total Fair Value	3,100	2,600
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	608	640
Unrealized Appreciation	346	242
Unrealized (Depreciation)	0	(2)
Total Fair Value	954	880
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,682	1,983
Unrealized Appreciation	176	167
Unrealized (Depreciation)	(2)	(6)
Total Fair Value	1,856	2,144
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,824	1,392
Unrealized Appreciation	121	64
Unrealized (Depreciation)	(5)	(12)
Total Fair Value	1,940	1,444
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,517	10,306
Unrealized Appreciation	1,014	749
Unrealized (Depreciation)	(33)	(74)
Total Fair Value	13,498	10,981
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83	153
Unrealized Appreciation	3	3
Unrealized (Depreciation)	(1)	(3)
Total Fair Value	85	153
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	564	799
Unrealized Appreciation	87	87
Unrealized (Depreciation)	(1)	(2)
Total Fair Value	$ 650	$ 884