Schedule III Supplementary Insurance Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	$ 11,042	$ 11,115
Liability for Unpaid Claims and Claims Adjustment Expense, Future Policy Benefits	119,281	118,527
Reserve for Unearned Premiums	19,634	21,318
Policy and Contract Claims	847	862
Premiums and Policy Fees	37,125	39,410	$ 39,869
Net Investment Income	14,065	14,053	16,079
Losses and Loss Expenses Incurred, Benefits	36,142	35,076	32,049
Amortization of Deferred Policy Acquisition Costs	4,521	5,236	5,330
Other Operating Expenses	8,682	10,434	10,489
Net Premiums Written	29,233	33,066	34,456
Commercial Insurance [Member]
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Policy Fees	18,100	19,715	20,407
Net Investment Income	3,268	3,421	4,255
Losses and Loss Expenses Incurred, Benefits	18,828	16,660	14,226
Amortization of Deferred Policy Acquisition Costs	2,049	2,349	2,497
Other Operating Expenses	3,226	3,562	3,692
Net Premiums Written	16,928	20,616	20,773
Consumer Insurance [Member]
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Policy Fees	15,426	15,070	15,791
Net Investment Income	7,345	7,356	7,924
Losses and Loss Expenses Incurred, Benefits	12,063	11,967	12,055
Amortization of Deferred Policy Acquisition Costs	2,681	2,762	2,655
Other Operating Expenses	5,456	6,872	6,797
Net Premiums Written	11,465	11,583	12,408
Other Operations
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Policy Fees	2,783	3,455	2,457
Net Investment Income	539	348	655
Losses and Loss Expenses Incurred, Benefits	1,900	2,845	2,299
Amortization of Deferred Policy Acquisition Costs	(317)	23	97
Other Operating Expenses	0	0	0
Net Premiums Written	819	668	1,032
Legacy portfolio [Member]
Supplementary Insurance Information, by Segment [Line Items]
Premiums and Policy Fees	816	1,170	1,214
Net Investment Income	2,913	2,928	3,245
Losses and Loss Expenses Incurred, Benefits	3,351	3,604	3,469
Amortization of Deferred Policy Acquisition Costs	108	102	81
Other Operating Expenses	0	0	0
Net Premiums Written	21	199	$ 243
Property Casualty Insurance Companies [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	2,563	2,631
Liability for Unpaid Claims and Claims Adjustment Expense, Future Policy Benefits	71,812	69,213
Reserve for Unearned Premiums	19,348	20,961
Policy and Contract Claims	0	0
Life Insurance Companies [Member]
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	8,466	8,467
Liability for Unpaid Claims and Claims Adjustment Expense, Future Policy Benefits	41,384	42,893
Reserve for Unearned Premiums	0	0
Policy and Contract Claims	836	851
Other
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	13	17
Liability for Unpaid Claims and Claims Adjustment Expense, Future Policy Benefits	6,085	6,421
Reserve for Unearned Premiums	286	357
Policy and Contract Claims	$ 11	$ 11