Commitments and Contingent Liabilities - Additional Information (Detail) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Loss Contingencies [Line Items]
Reserves on unfunded commitments, unused lines of credit, letters of credit and repurchase of sold loans classified in other liabilities	$ 2,000,000
Reserve for repurchase of sold loans	2,600,000
Retained secondary credit loss exposure	15,877,000	20,442,000
Net credit enhancement fee income	14,000	71,000	648,000
Unpaid principal balance of loans repurchased from investors	1,600,000	1,700,000	2,100,000
Asset disposition related expense	1,900,000	200,000.0	0.0
Possible losses due to an unfavorable outcome of pending lawsuit, minimum range	0
Possible losses due to an unfavorable outcome of pending lawsuit, maximum range	2,400,000
Residential Loans
Loss Contingencies [Line Items]
Retained secondary mortgage loans originated for FHLB	$ 276,400,000