Applicable Income Taxes Included in the Consolidated Statements of Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation Of Provision Of Income Taxes [Abstract]
U.S. Federal income taxes	$ 424us-gaap_CurrentFederalTaxExpenseBenefit	$ 494us-gaap_CurrentFederalTaxExpenseBenefit	$ 327us-gaap_CurrentFederalTaxExpenseBenefit
State and local income taxes	34	23	38
Foreign income taxes	8us-gaap_CurrentForeignTaxExpenseBenefit	2us-gaap_CurrentForeignTaxExpenseBenefit
Total current tax (benefit) expense	466us-gaap_CurrentIncomeTaxExpenseBenefit	519us-gaap_CurrentIncomeTaxExpenseBenefit	365us-gaap_CurrentIncomeTaxExpenseBenefit
U.S. Federal income taxes	71	232	252
State and local income taxes	9	23	19
Foreign income taxes	(1)	(2)
Total deferred tax expense (benefit)	79us-gaap_DeferredIncomeTaxExpenseBenefit	253us-gaap_DeferredIncomeTaxExpenseBenefit	271us-gaap_DeferredIncomeTaxExpenseBenefit
Applicable income tax expense	$ 545us-gaap_IncomeTaxExpenseBenefit	$ 772us-gaap_IncomeTaxExpenseBenefit	$ 636us-gaap_IncomeTaxExpenseBenefit

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