Investments - Appreciation (Depreciation) on Fixed Maturities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 17,252	$ 17,278
Unrealized Appreciation	1,936	1,747
Unrealized (Depreciation)	(47)	(42)
Total Fair Value	19,141	18,983
Run-off Settlement Annuity Business [Member]
Schedule of Available-for-sale Securities [Line Items]
Unrealized Appreciation	820	758
Unrealized (Depreciation)	(3)	(2)
Total Fair Value	3,200	3,100
Federal government and agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	568	608
Unrealized Appreciation	355	346
Unrealized (Depreciation)	0	0
Total Fair Value	923	954
State and local government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,662	1,682
Unrealized Appreciation	172	176
Unrealized (Depreciation)	(2)	(2)
Total Fair Value	1,832	1,856
Foreign government [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,807	1,824
Unrealized Appreciation	153	121
Unrealized (Depreciation)	(4)	(5)
Total Fair Value	1,956	1,940
Corporate [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,600	12,517
Unrealized Appreciation	1,159	1,014
Unrealized (Depreciation)	(38)	(33)
Total Fair Value	13,721	13,498
Mortgage-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62	83
Unrealized Appreciation	3	3
Unrealized (Depreciation)	(1)	(1)
Total Fair Value	64	85
Other asset-backed [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	553	564
Unrealized Appreciation	94	87
Unrealized (Depreciation)	(2)	(1)
Total Fair Value	$ 645	$ 650