Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
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	0	0	0	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	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	15	15	15	15
States, municipalities and political subdivisions [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	84	61	100	61
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)	1	(1)	(1)	(1)
Purchases and issuances	9	0	34	0
Sales and settlements	(1)	0	(1)	0
Transfer into Level 3	0	7	0	7
Transfer out of Level 3	0	0	(39)	0
Financial assets, Ending Balance	93	66	93	66
Residential Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	296	256	300	316
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(3)	0	(5)	3
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	(1)	0	5
Purchases and issuances	0	8	0	8
Sales and settlements	(8)	(8)	(24)	(23)
Transfer into Level 3	10	20	67	58
Transfer out of Level 3	0	(12)	(44)	(104)
Financial assets, Ending Balance	294	263	294	263
Commercial Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	48	28	44	28
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)	(1)	0	(1)	0
Purchases and issuances	0	0	0	0
Sales and settlements	(1)	0	(1)	0
Transfer into Level 3	0	0	4	0
Transfer out of Level 3	(1)	0	(1)	0
Financial assets, Ending Balance	45	27	45	27
Asset-backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	332	204	226	75
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	0	0	1	3
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	(3)	0	(2)
Purchases and issuances	110	8	230	68
Sales and settlements	(3)	(7)	(51)	(23)
Transfer into Level 3	20	0	53	81
Transfer out of Level 3	(10)	(23)	(10)	(23)
Financial assets, Ending Balance	449	179	449	179
All other corporate [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	597	313	546	335
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	0	(1)	(3)	4
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	7	1	(4)	4
Purchases and issuances	24	51	103	72
Sales and settlements	(13)	(13)	(37)	(59)
Transfer into Level 3	31	91	41	91
Transfer out of Level 3	0	0	0	(5)
Financial assets, Ending Balance	646	442	646	442
Equity securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	118	81	93	31
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	0	0	(4)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(2)	(2)	(1)	2
Purchases and issuances	7	2	52	48
Sales and settlements	0	0	0	(9)
Transfer into Level 3	0	0	0	22
Transfer out of Level 3	0	0	(17)	(14)
Financial assets, Ending Balance	123	81	123	81
Assets of Managed Investment Entities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	29	27	31	30
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(3)	0	(9)	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0	0
Purchases and issuances	0	3	4	3
Sales and settlements	0	(1)	0	(2)
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