Acquisitions and Discontinued Operations - Change in Fair Values of Level 3 Consolidated Education Loan Securitization Trusts and Portfolio Loans (Parenthetical) (Detail) (Education Lending [Member], Discontinued Operations [Member], USD $)	Mar. 31, 2015	Mar. 31, 2014
Education Lending [Member] | Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Issuances transfers	$ 0	$ 0