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, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	$ 1,281	$ 1,303
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	18	17
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	7	12
Purchases	125	178
Sales	(156)	(95)
Settlements	(53)	(110)
Transfers into Level 3	37	38
Transfers out of Level 3	(46)	(55)
Balance, Ending, Assets	1,213	1,288
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	1	1
Fixed maturity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	1,183	1,203
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	5	4
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	10	16
Purchases	125	178
Sales	(156)	(87)
Settlements	(37)	(99)
Transfers into Level 3	37	38
Transfers out of Level 3	(46)	(54)
Balance, Ending, Assets	1,121	1,199
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Corporate and other bonds [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	162	204
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	1
Purchases	12	5
Sales	(12)	(4)
Settlements	(14)	(5)
Transfers into Level 3	37	3
Transfers out of Level 3	0	(16)
Balance, Ending, Assets	186	189
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	94	71
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	0
Sales	0	0
Settlements	(9)	0
Transfers into Level 3	0	14
Transfers out of Level 3	0	0
Balance, Ending, Assets	86	86
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Residential mortgage-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	189	331
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	15
Purchases	72	25
Sales	0	0
Settlements	(10)	(21)
Transfers into Level 3	0	21
Transfers out of Level 3	(20)	(13)
Balance, Ending, Assets	232	359
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	83	151
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	1	(1)
Purchases	6	0
Sales	0	0
Settlements	(1)	(1)
Transfers into Level 3	0	0
Transfers out of Level 3	(26)	(24)
Balance, Ending, Assets	64	126
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Other asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	655	446
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	1	1
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	9	0
Purchases	35	148
Sales	(144)	(83)
Settlements	(3)	(72)
Transfers into Level 3	0	0
Transfers out of Level 3	0	(1)
Balance, Ending, Assets	553	439
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Total asset-backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	927	928
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	3	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	10	14
Purchases	113	173
Sales	(144)	(83)
Settlements	(14)	(94)
Transfers into Level 3	0	21
Transfers out of Level 3	(46)	(38)
Balance, Ending, Assets	849	924
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	0	0
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets	16	11
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	0	3
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	(3)	(4)
Purchases	0	0
Sales	0	(8)
Settlements	0	0
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	13	2
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	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	82	88
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)	13	10
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)	0	0
Purchases	0	0
Sales	0	0
Settlements	(16)	(11)
Transfers into Level 3	0	0
Transfers out of Level 3	0	0
Balance, Ending, Assets	79	87
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)	1	1
Separate account business [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, Beginning, Assets		1
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in net income (loss)		0
Net change in unrealized appreciation (depreciation) included in other comprehensive income (loss)		0
Purchases		0
Sales		0
Settlements		0
Transfers into Level 3		0
Transfers out of Level 3		(1)
Balance, Ending, Assets		0
Unrealized gains (losses) on Level 3 assets and liabilities held at balance sheet date recognized in net income (loss)		$ 0