Fair Value Measurements (Details 2) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	$ 1,636	$ 1,355
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	(20)	(3)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	20	7
Purchases and issuances	102	59
Sales and settlements	(23)	(61)
Transfer into Level 3	72	62
Transfer out of Level 3	(16)	(86)
Financial assets, Ending Balance	1,771	1,333
US Treasury and Government [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	15	15
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	15	15
States, municipalities and political subdivisions [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	89	100
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	3	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	(39)
Financial assets, Ending Balance	92	61
Residential Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	224	300
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	1	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	3
Purchases and issuances	0	0
Sales and settlements	(7)	(7)
Transfer into Level 3	11	41
Transfer out of Level 3	(16)	(30)
Financial assets, Ending Balance	213	306
Commercial Mortgage Backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	39	44
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	(1)	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	38	44
Asset-backed Securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	470	226
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	0	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(6)	0
Purchases and issuances	4	5
Sales and settlements	(8)	(41)
Transfer into Level 3	41	21
Transfer out of Level 3	0	0
Financial assets, Ending Balance	501	211
All other corporate [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	633	546
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	(2)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	15	6
Purchases and issuances	86	44
Sales and settlements	(7)	(13)
Transfer into Level 3	5	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	730	583
Fixed maturities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	1,470	1,231
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	(1)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	12	9
Purchases and issuances	90	49
Sales and settlements	(23)	(61)
Transfer into Level 3	57	62
Transfer out of Level 3	(16)	(69)
Financial assets, Ending Balance	1,589	1,220
Equity securities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	140	93
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	(17)	0
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	8	(2)
Purchases and issuances	12	10
Sales and settlements	0	0
Transfer into Level 3	15	0
Transfer out of Level 3	0	(17)
Financial assets, Ending Balance	158	84
Assets of Managed Investment Entities [Member]
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Financial assets, Beginning Balance	26	31
Impact of accounting change		0
Total realized/unrealized gains (losses) included in Net income	(2)	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0
Purchases and issuances	0	0
Sales and settlements	0	0
Transfer into Level 3	0	0
Transfer out of Level 3	0	0
Financial assets, Ending Balance	$ 24	$ 29