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	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 473	$ 1,281
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	39
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	(8)
Purchases	296	303
Sales	(61)	(276)
Settlements	(157)	(182)
Transfers into Level 3	61	79
Transfers out of Level 3	(206)	(763)
Balance, Ending, Assets	407	473
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(5)	(1)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	168	162
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	(2)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(3)
Purchases	163	65
Sales	(36)	(13)
Settlements	(103)	(35)
Transfers into Level 3	0	40
Transfers out of Level 3	(64)	(46)
Balance, Ending, Assets	130	168
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(2)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	2	94
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(1)	(10)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(83)
Balance, Ending, Assets	1	2
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	134	189
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	3	5
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(5)	(3)
Purchases	15	81
Sales	0	0
Settlements	(14)	(35)
Transfers into Level 3	56	14
Transfers out of Level 3	(60)	(117)
Balance, Ending, Assets	129	134
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	22	83
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	7
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(4)
Purchases	32	23
Sales	0	0
Settlements	(17)	(17)
Transfers into Level 3	3	17
Transfers out of Level 3	(25)	(87)
Balance, Ending, Assets	13	22
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Other asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	53	655
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(2)	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	3
Purchases	86	130
Sales	(25)	(263)
Settlements	(1)	(52)
Transfers into Level 3	2	7
Transfers out of Level 3	(57)	(430)
Balance, Ending, Assets	57	53
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	209	927
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	15
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(5)	(4)
Purchases	133	234
Sales	(25)	(263)
Settlements	(32)	(104)
Transfers into Level 3	61	38
Transfers out of Level 3	(142)	(634)
Balance, Ending, Assets	199	209
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	379	1,183
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	14
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(4)	(7)
Purchases	296	299
Sales	(61)	(276)
Settlements	(136)	(149)
Transfers into Level 3	61	78
Transfers out of Level 3	(206)	(763)
Balance, Ending, Assets	330	379
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(2)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	20	16
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	(1)	0
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	(1)
Purchases	0	4
Sales	0	0
Settlements	0	0
Transfers into Level 3	0	1
Transfers out of Level 3	0	0
Balance, Ending, Assets	19	20
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(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	74	82
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	25
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(21)	(33)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	58	74
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (3)	$ 1