Acquisitions and Discontinued Operations - Components of Income (Loss) from Discontinued Operations, Net of Taxes, of Education Lending Business Acquisitions and Discontinued Operations (Parenthetical) (Detail) (Segment, discontinued operations [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Charges determined by applying a matched funds transfer pricing methodology to the liabilities assumed necessary to support the discontinued operations, after tax	$ 50	$ 50	$ 58
Education lending [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Charges determined by applying a matched funds transfer pricing methodology to the liabilities assumed necessary to support the discontinued operations, after tax	$ 50	$ 50	$ 58