Derivative Financial Instruments (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($) contract	Dec. 31, 2014 USD ($) contract
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Assumed recoveries under sale of credit protection	$ 0
Securities pledged in the form of margin deposits	30
Derivatives, Fair Value
Total asset derivatives, Notional amount	380	$ 407
Total liability derivatives, Notional amount	3,068	3,242
Total derivatives, Notional amount	$ 3,448	$ 3,649
Total asset derivatives, Number of contracts | contract	3,605	3,929
Total liability derivatives, Number of contracts | contract	3,995	3,331
Total derivatives, Number of contracts | contract	7,600	7,260
Net amount on balance sheet	$ 63	$ 92
Net amount on balance sheet	(324)	(354)
Total derivatives, Fair value, net	(261)	(262)
Asset derivatives, Gross asset	64	92
Counter- party netting	5	2
Counter- party netting	(1)	0
Liability derivatives, Gross liability	(329)	(356)
Derivatives not designated as accounting hedging instruments
Derivatives, Fair Value
Total asset derivatives, Notional amount	362	322
Total liability derivatives, Notional amount	$ 3,012	$ 3,192
Total asset derivatives, Number of contracts | contract	3,605	3,929
Total liability derivatives, Number of contracts | contract	3,995	3,331
Net amount on balance sheet	$ 60	$ 89
Net amount on balance sheet	(328)	(353)
Asset derivatives, Gross asset	61	89
Counter- party netting	1	2
Counter- party netting	(1)	0
Liability derivatives, Gross liability	(329)	(355)
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	18	85
Net amount on balance sheet	3	3
Asset derivatives, Gross asset	3	3
Counter- party netting	0	0
Foreign currency swap agreements | Derivatives designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	56	50
Net amount on balance sheet	4	(1)
Counter- party netting	4	0
Liability derivatives, Gross liability	0	(1)
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	152	163
Net amount on balance sheet	2	2
Asset derivatives, Gross asset	2	2
Counter- party netting	0	0
Interest rate cap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		11
Net amount on balance sheet		0
Counter- party netting		0
Liability derivatives, Gross liability		0
Interest rate swap agreements | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	85	85
Net amount on balance sheet	1	1
Counter- party netting	1	1
Liability derivatives, Gross liability	0	0
Options | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	3,110	3,225
Net amount on balance sheet	$ 55	$ 83
Asset derivatives, Gross asset	55	83
Counter- party netting	0	0
Financial futures contracts | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0
Total asset derivatives, Number of contracts | contract	475
Net amount on balance sheet	$ 0
Asset derivatives, Gross asset	0
Counter- party netting	0
Financial futures contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	$ 0	$ 0
Total asset derivatives, Number of contracts | contract	20	704
Net amount on balance sheet	$ 0	$ 1
Asset derivatives, Gross asset	0	1
Counter- party netting	0	0
Financial futures contracts | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		$ 0
Total liability derivatives, Number of contracts | contract		200
Net amount on balance sheet		$ 0
Counter- party netting		0
Liability derivatives, Gross liability		0
Options and futures | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	$ 0	$ 0
Total liability derivatives, Number of contracts | contract	3,995	3,131
Net amount on balance sheet	$ (5)	$ (22)
Counter- party netting	0	0
Liability derivatives, Gross liability	(5)	(22)
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	102	57
Net amount on balance sheet	1	0
Asset derivatives, Gross asset	1	0
Counter- party netting	0	0
Foreign currency forwards | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount		36
Net amount on balance sheet		1
Counter- party netting		1
Liability derivatives, Gross liability		0
Guaranteed accumulation benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	558	615
Net amount on balance sheet	(31)	(32)
Counter- party netting	0	0
Liability derivatives, Gross liability	(31)	(32)
Guaranteed withdrawal benefits | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	383	425
Net amount on balance sheet	(13)	(13)
Counter- party netting	0	0
Liability derivatives, Gross liability	(13)	(13)
Equity-indexed and forward starting options in life and annuity product contracts | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	1,786	1,786
Net amount on balance sheet	(270)	(278)
Counter- party netting	0	0
Liability derivatives, Gross liability	(270)	(278)
Other embedded derivative financial instruments | Derivatives not designated as accounting hedging instruments | Contractholder funds
Derivatives, Fair Value
Total liability derivatives, Notional amount	85	85
Net amount on balance sheet	(1)	0
Counter- party netting	0	0
Liability derivatives, Gross liability	(1)	0
Credit default swaps – buying protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	25	19
Net amount on balance sheet	0	0
Asset derivatives, Gross asset	1	0
Counter- party netting	(1)	0
Credit default swaps – buying protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	15	49
Net amount on balance sheet	(1)	(1)
Counter- party netting	0	0
Liability derivatives, Gross liability	(1)	(1)
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other investments
Derivatives, Fair Value
Total asset derivatives, Notional amount	80	80
Net amount on balance sheet	1	2
Asset derivatives, Gross asset	1	2
Counter- party netting	0	0
Credit default swaps – selling protection | Derivatives not designated as accounting hedging instruments | Other liabilities & accrued expenses
Derivatives, Fair Value
Total liability derivatives, Notional amount	100	100
Net amount on balance sheet	(8)	(9)
Counter- party netting	0	0
Liability derivatives, Gross liability	(8)	(9)
Other contracts | Derivatives not designated as accounting hedging instruments | Other assets
Derivatives, Fair Value
Total asset derivatives, Notional amount	3	3
Net amount on balance sheet	1	1
Asset derivatives, Gross asset	1	1
Counter- party netting	$ 0	$ 0