Provision for Federal & Foreign Income Tax Expense (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Federal income tax expense (benefit):
Current	$ 1,817	$ 2,020	$ 1,204
Deferred	(473)	(387)	3
Total federal income tax expense	1,344	1,633	1,207
Foreign income tax expense (benefit):
Current	46	24	6
Deferred	28	(13)	(8)
Total foreign income tax expense (benefit)	74	11	(2)
Total income tax expense	$ 1,418	$ 1,644	$ 1,205