Loans Receivable - Additional Information (Detail) (USD $)	12 Months Ended															12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		9 Months Ended	12 Months Ended				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2013 Multi Family Real Estate Properties [Member]	Mar. 31, 2013 Minimum	Mar. 31, 2013 Maximum	Mar. 31, 2013 Fixed-rate residential loans	Mar. 31, 2013 Fixed-rate residential loans Minimum	Mar. 31, 2013 Fixed-rate residential loans Maximum	Mar. 31, 2013 Residential Loans	Mar. 31, 2013 Residential Loans Minimum	Mar. 31, 2013 Residential Loans Maximum	Mar. 31, 2013 Adjustable Rate Residential Mortgage	Mar. 31, 2013 Commercial and Industrial Loans	Mar. 31, 2013 Commercial and Industrial Loans Maximum	Mar. 31, 2013 Commercial Real Estate Loans	Mar. 31, 2013 Commercial Real Estate Loans Minimum	Mar. 31, 2013 Commercial Real Estate Loans Maximum	Mar. 31, 2013 Consumer	Mar. 31, 2012 Consumer	Mar. 31, 2013 Consumer Minimum	Mar. 31, 2013 Consumer Maximum	Mar. 31, 2013 Education Loans	Mar. 31, 2011 Education Loans	Mar. 31, 2012 Education Loans	Mar. 31, 2013 Undergraduate studies	Mar. 31, 2013 Graduate studies	Mar. 31, 2013 Home Equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Refinance loans							$ 200,000			$ 203,900,000			$ 547,700,000			$ 343,800,000	$ 30,600,000		$ 770,900,000			$ 414,000,000				$ 166,400,000
Unpaid principal balance receivable of total loans, percentage										37.20%			31.10%			62.80%	1.70%		43.70%			23.50%				9.40%
Number of dwellings														1	4
Term of loans										15 years	10 Years	30 Years				30-year		7 Years
Interest rate of loans, minimum	2.00%
Interest rate of loans, maximum	6.00%
Amortization periods of loans								15 years	25 years											15 years	25 years
Balloon payments								2 years	5 years											2 years	7 years
Maximum loans made available for education																													3,500	8,500
Repayment status of loans on installment basis																										9 months
Guarantee given for principal amount and interest rate of loans, percentage																										97.00%
Sale of loans																										0		0
Proceeds from sale of education loan	943,429,000		947,833,000		809,971,000																						24,300,000
Appraised value of property at loan origination date, percentage																															90.00%
Amortization Period							15 years
Credit extended for outstanding balances																								25.00%	28.00%
Corporation's share of annual fees																								33.00%	37.00%
Corporation's share of interchanging income																								25.00%	30.00%
Corporation's share of late payment																						30.00%
Provision for unfunded commitment losses	1,392,000	[1]	(309,000)	[1]	873,000	[1]
Reserve for unfunded commitments and letters of credit	2,000,000
Unpaid principal balance of loans identified as impaired	160,355,000		297,572,000																			4,677,000	8,514,000
Value of unpaid principal balance receivable of classified loans as substandard	206,600,000
Percentage of unpaid principal balance receivable classified as substandard	90.00%
Time period of appraised values for real estate	1 year
Discounting of appraised value by additional percentage, improved land or commercial real estate	10.00%
Discounting of appraised value by additional percentage, unimproved land	20.00%
Loans not requiring appraisal, small loans	250,000
Percentage of loans which not require an updated appraisal	46.00%
Period of delinquent loans			30 days
Total delinquencies	116,600,000
Education loan due	13,700,000
Period of delinquent loans considered as non accrual			90 days
Guarantee provided by government agencies against outstanding balances of education loans	97.00%		97.00%
Maximum value of non accrual loans for performing the individual impairment evaluation	500,000
Unpaid principal of various loans receivable	823,700,000		859,800,000
Loans granted to officers, directors and affiliates	91,000		215,000
Principal additions to granted loan	0
Principal loan amount, net	$ 124,000

[1] The provision for unfunded commitments includes provisions for unfunded commitments to lend and commercial letters of credit.