Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 520	$ 1,101	$ 473	$ 1,281
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	12	12	36
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	7	(13)	14	(6)
Purchases	78	82	279	263
Sales	0	(21)	(61)	(267)
Settlements	(15)	(71)	(61)	(169)
Transfers into Level 3	0	0	5	54
Transfers out of Level 3	(96)	(41)	(167)	(143)
Balance, Ending, Assets	494	1,049	494	1,049
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(2)	2	0	0
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	242	141	168	162
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	0	1	(1)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	7	0	14	(1)
Purchases	16	27	163	39
Sales	0	(1)	(36)	(13)
Settlements	(5)	(11)	(15)	(32)
Transfers into Level 3	0	0	0	37
Transfers out of Level 3	0	(3)	(34)	(38)
Balance, Ending, Assets	261	153	261	153
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	2	85	2	94
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	0	0	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	(1)	0	(1)	(10)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(24)	0	(24)
Balance, Ending, Assets	1	61	1	61
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	134	207	134	189
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	2	2	4
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(2)	(2)	(4)
Purchases	5	4	15	76
Sales	0	0	0	0
Settlements	(1)	(7)	(10)	(28)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	(58)	0	(60)	(33)
Balance, Ending, Assets	79	204	79	204
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	11	87	22	83
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	5	0	7
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	(4)	0	(4)
Purchases	23	8	32	23
Sales	0	0	0	0
Settlements	(8)	(15)	(17)	(17)
Transfers into Level 3	0	0	3	17
Transfers out of Level 3	(2)	(10)	(16)	(38)
Balance, Ending, Assets	24	71	24	71
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Other asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	45	490	53	655
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	0	0	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	(6)	2	4
Purchases	34	43	69	125
Sales	0	(20)	(25)	(254)
Settlements	0	(32)	(1)	(52)
Transfers into Level 3	0	0	2	0
Transfers out of Level 3	(36)	(4)	(57)	(10)
Balance, Ending, Assets	43	471	43	471
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	(1)
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	190	784	209	927
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	7	2	14
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(12)	0	(4)
Purchases	62	55	116	224
Sales	0	(20)	(25)	(254)
Settlements	(9)	(54)	(28)	(97)
Transfers into Level 3	0	0	5	17
Transfers out of Level 3	(96)	(14)	(133)	(81)
Balance, Ending, Assets	146	746	146	746
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	(1)
Total Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	434	1,010	379	1,183
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	7	3	14
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	6	(12)	14	(5)
Purchases	78	82	279	263
Sales	0	(21)	(61)	(267)
Settlements	(15)	(65)	(44)	(139)
Transfers into Level 3	0	0	5	54
Transfers out of Level 3	(96)	(41)	(167)	(143)
Balance, Ending, Assets	408	960	408	960
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	(1)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	19	16	20	16
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	0	(1)	0
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(1)	0	(1)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	19	15	19	15
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(2)	0	(2)	0
Life settlement contracts, included in Other assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	67	75	74	82
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	5	10	22
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	(6)	(17)	(30)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	67	74	67	74
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ 0	$ 2	$ 2	$ 1