Fair Value Measurements (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
US Treasury and Government [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	$ 15	$ 15	$ 20
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	0	0	(2)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	(3)
Purchases and issuances	0	0	0
Sales and settlements	0	0	0
Transfer into Level 3	0	0	0
Transfer out of Level 3	0	0	0
Sale of subsidiaries	0
Financial assets, Ending Balance	15	15	15
States, municipalities and political subdivisions [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	100	61	58
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	0	(1)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	0	(2)
Purchases and issuances	34	30	10
Sales and settlements	(1)	0	0
Transfer into Level 3	2	10	0
Transfer out of Level 3	(39)	0	(4)
Sale of subsidiaries	(6)
Financial assets, Ending Balance	89	100	61
Residential Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	300	316	371
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	(11)	4	5
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	3	24
Purchases and issuances	0	13	6
Sales and settlements	(34)	(31)	(53)
Transfer into Level 3	86	111	86
Transfer out of Level 3	(88)	(116)	(123)
Sale of subsidiaries	(28)
Financial assets, Ending Balance	224	300	316
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	44	28	22
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	(1)	(1)	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(1)	0	(1)
Purchases and issuances	0	0	0
Sales and settlements	(2)	0	0
Transfer into Level 3	4	17	8
Transfer out of Level 3	(1)	0	0
Sale of subsidiaries	(4)
Financial assets, Ending Balance	39	44	28
Asset-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	226	75	253
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	1	3	4
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(7)	(2)	(3)
Purchases and issuances	265	99	12
Sales and settlements	(56)	(39)	(57)
Transfer into Level 3	53	117	11
Transfer out of Level 3	(10)	(27)	(145)
Sale of subsidiaries	(2)
Financial assets, Ending Balance	470	226	75
All other corporate [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	546	335	236
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	(5)	2	1
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(9)	13	(14)
Purchases and issuances	161	102	113
Sales and settlements	(90)	(73)	(17)
Transfer into Level 3	41	172	24
Transfer out of Level 3	(5)	(5)	(8)
Sale of subsidiaries	(6)
Financial assets, Ending Balance	633	546	335
Equity securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	93	31	37
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	(4)	1	(1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	(9)	2	6
Purchases and issuances	77	62	53
Sales and settlements	0	(9)	(12)
Transfer into Level 3	0	22	0
Transfer out of Level 3	(17)	(16)	(52)
Sale of subsidiaries	0
Financial assets, Ending Balance	140	93	31
Assets of Managed Investment Entities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial assets, Beginning Balance	31	30	40
Impact of accounting change	0
Total realized/unrealized gains (losses) included in Net income	(11)	(3)	(5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss)	0	0	0
Purchases and issuances	6	6	8
Sales and settlements	0	(2)	(7)
Transfer into Level 3	0	0	0
Transfer out of Level 3	0	0	(6)
Sale of subsidiaries	0
Financial assets, Ending Balance	$ 26	$ 31	$ 30