Income Taxes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010 Other matter	Dec. 31, 2010 Leveraged leases
Income Taxes [Line Items]
Favorable impact on income tax, settled its outstanding dispute with the Internal Revenue Service (IRS)			$ 19	$ 6
Accrued interest liabilities, net of the related tax benefits	3	3
Retained earnings included allocation of earnings for bad debt deductions of former thrift subsidiaries	157	157
Deferred tax assets related to state net operating loss carryforwards	33	63
Operating loss carryforwards valuation allowances	20	34
Operating loss carryforwards expiration date	2030
Tax credit carryforwards		$ 5