Schedule III (details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule III
Deferred acquisition costs	$ 1,804	$ 1,792	$ 1,786
Claims and claim adjustment expense reserves	50,895	50,922	51,392
Unearned premiums	11,850	11,241	11,102
Earned premiums	22,637	22,357	22,090
Net investment income	2,716	2,889	2,879
Claims and claim adjustment expenses	13,307	14,676	16,276
Amortization of deferred acquisition costs	3,821	3,910	3,876
Other operating expenses	4,118	3,988	3,942
Net written premiums	22,767	22,447	22,187
Reportable Segments [Member]
Schedule III
Deferred acquisition costs	1,804	1,792	1,786
Claims and claim adjustment expense reserves	50,865	50,888	51,353
Unearned premiums	11,850	11,241	11,102
Earned premiums	22,637	22,357	22,090
Net investment income	2,716	2,889	2,879
Claims and claim adjustment expenses	13,307	14,676	16,276
Amortization of deferred acquisition costs	3,821	3,910	3,876
Other operating expenses	3,737	3,587	3,500
Net written premiums	22,767	22,447	22,187
Reportable Segments [Member] | Business Insurance [Member]
Schedule III
Deferred acquisition costs	847	843	816
Claims and claim adjustment expense reserves	38,777	39,598	40,129
Unearned premiums	5,888	5,728	5,482
Earned premiums	12,084	11,691	11,327
Net investment income	1,975	2,090	2,041
Claims and claim adjustment expenses	7,576	7,857	8,447
Amortization of deferred acquisition costs	1,913	1,884	1,815
Other operating expenses	2,052	2,020	1,944
Net written premiums	12,233	11,872	11,340
Reportable Segments [Member] | Financial, Professional & International Insurance [Member]
Schedule III
Deferred acquisition costs	412	325	332
Claims and claim adjustment expense reserves	8,325	6,445	6,857
Unearned premiums	2,546	1,964	2,043
Earned premiums	3,229	3,045	3,174
Net investment income	372	395	414
Claims and claim adjustment expenses	1,404	1,314	1,487
Amortization of deferred acquisition costs	623	589	603
Other operating expenses	705	667	648
Net written premiums	3,309	2,981	3,102
Reportable Segments [Member] | Personal Insurance [Member]
Schedule III
Deferred acquisition costs	545	624	638
Claims and claim adjustment expense reserves	3,763	4,845	4,367
Unearned premiums	3,416	3,549	3,577
Earned premiums	7,324	7,621	7,589
Net investment income	369	404	424
Claims and claim adjustment expenses	4,327	5,505	6,342
Amortization of deferred acquisition costs	1,285	1,437	1,458
Other operating expenses	980	900	908
Net written premiums	7,225	7,594	7,745
Other [Member]
Schedule III
Claims and claim adjustment expense reserves	30	34	39
Other operating expenses	$ 381	$ 401	$ 442