Fair Value of Financial Instruments - Additional Information (Detail)	12 Months Ended
	Mar. 31, 2013
Non-agency CMOs
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Financial assets valued by independent pricing service	99.30%
Mortgage Servicing Rights | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	10.00%
Total portfolio lifetime weighted average prepayment speeds	7.50%
Mortgage Servicing Rights | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	23.50%
Total portfolio lifetime weighted average prepayment speeds	37.60%