Schedule of Effects of Reinsurance Premiums for Insurance Companies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property-liability insurance premiums earned
Direct	$ 34,015	$ 32,915	$ 31,858
Assumed	863	890	674
Ceded	(1,296)	(1,338)	(1,446)
Net amount	33,582	32,467	31,086
Life and annuity premiums and contract charges
Life and annuity premiums and contract charges, net of reinsurance	2,275	2,158	2,157
Property-liability insurance premiums earned
Property-liability insurance premiums written
Direct	32,614	31,924	30,686
Assumed	47	39	48
Ceded	(1,061)	(1,092)	(1,120)
Property-liability insurance premiums written, net of reinsurance	31,600	30,871	29,614
Property-liability insurance premiums earned
Direct	32,249	31,274	29,914
Assumed	45	41	45
Ceded	(987)	(1,006)	(1,030)
Net amount	31,307	30,309	28,929
Life and annuity premiums and contract charges
Life and annuity premiums and contract charges
Direct	1,766	1,641	1,944
Assumed	818	849	629
Ceded	(309)	(332)	(416)
Life and annuity premiums and contract charges, net of reinsurance	$ 2,275	$ 2,158	$ 2,157