Federal and Foreign Income Tax - Tax Effects of Temporary Differences that Gave Rise to Deferred Income Tax Assets and Liabilities (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Deferred income tax assets
Unpaid losses and loss expenses	$ 524	$ 605
Unearned premiums	350	341
Foreign tax credits	867	870
Employee compensation	142	119
Postretirement benefits	95	324
Other-than-temporary impairment losses	291	294
Total deferred income tax assets	2,269	2,553
Deferred income tax liabilities
Deferred policy acquisition costs	356	341
Unremitted earnings of foreign subsidiaries	970	951
Unrealized appreciation of investments	660	1,084
Other invested assets	184	225
Other, net	52	114
Total deferred income tax liabilities	2,222	2,715
Net deferred income tax asset (liability)	$ 47	$ (162)