Applicable Income Taxes Included in the Consolidated Statements of Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation Of Provision Of Income Taxes [Line Items]
U.S. Federal income taxes	$ 327	$ 82	$ (5)
State and local income taxes	38	14	16
Total current tax (benefit) expense	365	96	11
U.S. Federal income taxes	252	411	165
State and local income taxes	19	26	11
Total deferred tax expense (benefit)	271	437	176
Applicable income tax expense	$ 636	$ 533	$ 187