Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 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	61	61	100	61
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)	(2)	0	(2)	0
Purchases and issuances	25	0	25	0
Sales and settlements	0	0	0	0
Transfer into Level 3	0	0	0	0
Transfer out of Level 3	0	0	(39)	0
Financial assets, Ending Balance	84	61	84	61
Residential Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	306	272	300	316
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(1)	2	(2)	3
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(2)	2	1	6
Purchases and issuances	0	0	0	0
Sales and settlements	(9)	(7)	(16)	(15)
Transfer into Level 3	16	6	57	38
Transfer out of Level 3	(14)	(19)	(44)	(92)
Financial assets, Ending Balance	296	256	296	256
Commercial Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	44	28	44	28
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	4	0	4	0
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	48	28	48	28
Asset-backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	211	206	226	75
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	1	3	1	3
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0	1
Purchases and issuances	115	10	120	60
Sales and settlements	(7)	(15)	(48)	(16)
Transfer into Level 3	12	0	33	81
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	332	204	332	204
All other corporate [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	583	322	546	335
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(3)	4	(3)	5
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(17)	0	(11)	3
Purchases and issuances	35	20	79	21
Sales and settlements	(11)	(30)	(24)	(46)
Transfer into Level 3	10	0	10	0
Transfer out of Level 3	0	(3)	0	(5)
Financial assets, Ending Balance	597	313	597	313
Equity securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	84	41	93	31
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(4)	0	(4)	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	3	2	1	4
Purchases and issuances	35	16	45	46
Sales and settlements	0	0	0	(9)
Transfer into Level 3	0	22	0	22
Transfer out of Level 3	0	0	(17)	(14)
Financial assets, Ending Balance	118	81	118	81
Assets of Managed Investment Entities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	29	29	31	30
Impact of accounting change			0
Total realized/unrealized gains (losses) included in Net income	(4)	(1)	(6)	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0	0
Purchases and issuances	4	0	4	0
Sales and settlements	0	(1)	0	(1)
Transfer into Level 3	0	0	0	0
Transfer out of Level 3	0	0	0	0
Financial assets, Ending Balance	$ 29	$ 27	$ 29	$ 27