Income Taxes (Applicable Income Taxes Included in the Consolidated Statements of Income) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation Of Provision Of Income Taxes
U.S. Federal income taxes	$ 763	$ 598	$ 662
State and local income taxes	68	55	55
Foreign income taxes	(3)	0	13
Total current tax expense (benefit)	828	653	730
U.S. Federal income taxes	(252)	(133)	(78)
State and local income taxes	1	(14)	6
Foreign income taxes	0	(1)	1
Total deferred tax expense (benefit)	(251)	(148)	(71)
Applicable income tax expense	$ 577	$ 505	$ 659