Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	$ 1,771	$ 1,333	$ 1,636	$ 1,355
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	(8)	(11)	(28)	(14)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	25	(18)	45	(11)
Purchases and issuances	23	214	125	273
Sales and settlements	(87)	(27)	(110)	(88)
Transfer into Level 3	32	42	104	104
Transfer out of Level 3	(31)	(14)	(47)	(100)
Financial assets, Ending Balance	1,725	1,519	1,725	1,519
US Treasury and Government [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	15	15	15	15
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	(8)	0	(8)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	1	0	1	0
Purchases and issuances	0	0	0	0
Sales and settlements	0	0	0	0
Transfer into Level 3	0	0	0	0
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	8	15	8	15
States, municipalities and political subdivisions [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	92	61	89	100
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	0	0	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	(2)	3	(2)
Purchases and issuances	0	25	0	25
Sales and settlements	(1)	0	(1)	0
Transfer into Level 3	0	0	0	0
Transfer out of Level 3	0	0	0	(39)
Financial assets, Ending Balance	91	84	91	84
Residential Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	213	306	224	300
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	1	(1)	2	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	1	(2)	1	1
Purchases and issuances	0	0	0	0
Sales and settlements	(6)	(9)	(13)	(16)
Transfer into Level 3	22	16	33	57
Transfer out of Level 3	0	(14)	(16)	(44)
Financial assets, Ending Balance	231	296	231	296
Commercial Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	38	44	39	44
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	(1)	0	(1)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0	0
Purchases and issuances	0	0	0	0
Sales and settlements	(1)	0	(2)	0
Transfer into Level 3	0	4	0	4
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	36	48	36	48
Asset-backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	501	211	470	226
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	0	1	0	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	3	0	(3)	0
Purchases and issuances	11	115	15	120
Sales and settlements	(11)	(7)	(19)	(48)
Transfer into Level 3	0	12	41	33
Transfer out of Level 3	(26)	0	(26)	0
Financial assets, Ending Balance	478	332	478	332
All other corporate [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	730	583	633	546
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	2	(3)	0	(3)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	12	(17)	27	(11)
Purchases and issuances	8	35	94	79
Sales and settlements	(68)	(11)	(75)	(24)
Transfer into Level 3	10	10	15	10
Transfer out of Level 3	(5)	0	(5)	0
Financial assets, Ending Balance	689	597	689	597
Fixed maturities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	1,589	1,220	1,470	1,231
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	(6)	(3)	(7)	(4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	17	(21)	29	(12)
Purchases and issuances	19	175	109	224
Sales and settlements	(87)	(27)	(110)	(88)
Transfer into Level 3	32	42	89	104
Transfer out of Level 3	(31)	(14)	(47)	(83)
Financial assets, Ending Balance	1,533	1,372	1,533	1,372
Equity securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	158	84	140	93
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	0	(4)	(17)	(4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	8	3	16	1
Purchases and issuances	0	35	12	45
Sales and settlements	0	0	0	0
Transfer into Level 3	0	0	15	0
Transfer out of Level 3	0	0	0	(17)
Financial assets, Ending Balance	166	118	166	118
Assets of Managed Investment Entities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	24	29	26	31
Impact of accounting change				0
Total realized/unrealized gains (losses) included in Net income	(2)	(4)	(4)	(6)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0	0
Purchases and issuances	4	4	4	4
Sales and settlements	0	0	0	0
Transfer into Level 3	0	0	0	0
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	$ 26	$ 29	$ 26	$ 29