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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 491	$ 1,213	$ 473	$ 1,281
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	8	6	12	24
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	0	7	7
Purchases	139	56	201	181
Sales	(45)	(90)	(61)	(246)
Settlements	(32)	(45)	(46)	(98)
Transfers into Level 3	3	17	5	54
Transfers out of Level 3	(48)	(56)	(71)	(102)
Balance, Ending, Assets	520	1,101	520	1,101
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	(3)	(5)	(3)	(4)
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	193	186	168	162
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	(2)	0	(1)
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	3	(1)	7	(1)
Purchases	94	0	147	12
Sales	(20)	0	(36)	(12)
Settlements	(7)	(7)	(10)	(21)
Transfers into Level 3	0	0	0	37
Transfers out of Level 3	(22)	(35)	(34)	(35)
Balance, Ending, Assets	242	141	242	141
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(3)	0	(3)
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	2	86	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	0	(1)	0	(10)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	2	85	2	85
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	128	232	134	189
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	1	2	2
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(1)	(2)	(1)	(2)
Purchases	10	0	10	72
Sales	0	0	0	0
Settlements	(4)	(11)	(9)	(21)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	(13)	(2)	(33)
Balance, Ending, Assets	134	207	134	207
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	27	64	22	83
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	1	0	2
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	(1)	0	0
Purchases	0	9	9	15
Sales	0	0	0	0
Settlements	(9)	(1)	(9)	(2)
Transfers into Level 3	3	17	3	17
Transfers out of Level 3	(10)	(2)	(14)	(28)
Balance, Ending, Assets	11	87	11	87
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	50	553	53	655
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	2	0	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	2	1	2	10
Purchases	35	47	35	82
Sales	(25)	(90)	(25)	(234)
Settlements	(1)	(17)	(1)	(20)
Transfers into Level 3	0	0	2	0
Transfers out of Level 3	(16)	(6)	(21)	(6)
Balance, Ending, Assets	45	490	45	490
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	205	849	209	927
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	4	2	7
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(2)	1	8
Purchases	45	56	54	169
Sales	(25)	(90)	(25)	(234)
Settlements	(14)	(29)	(19)	(43)
Transfers into Level 3	3	17	5	17
Transfers out of Level 3	(26)	(21)	(37)	(67)
Balance, Ending, Assets	190	784	190	784
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	0
Total Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	400	1,121	379	1,183
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	2	2	2	7
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	4	(3)	8	7
Purchases	139	56	201	181
Sales	(45)	(90)	(61)	(246)
Settlements	(21)	(37)	(29)	(74)
Transfers into Level 3	3	17	5	54
Transfers out of Level 3	(48)	(56)	(71)	(102)
Balance, Ending, Assets	434	1,010	434	1,010
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	(3)	0	(3)
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	19	13	20	16
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	0	0	0
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	3	(1)	0
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	16	19	16
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	0	0	0	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	72	79	74	82
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	6	4	10	17
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	(11)	(8)	(17)	(24)
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Balance, Ending, Assets	67	75	67	75
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	$ (3)	$ (2)	$ (3)	$ (1)