Unpaid Principal Balance of Loans Modified in TDR by Class and by Type of Modification (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only	$ 540	[1],[2]	$ 6,371	[1],[2]
Interest Rate Reduction, To Below Market Rate	336	[1],[2]	41,081	[1],[2]
Interest Rate Reduction, To Interest Only	160	[1],[2],[3]	3,253	[1],[2],[3]
Below Market Rate	460	[1],[2],[4]	24,575	[1],[2],[4]
Other	1,084	[1],[2],[5]	20,498	[1],[2],[5]
Total	2,580	[1],[2]	95,778	[1],[2]
Residential
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only			1,400	[1],[2]
Interest Rate Reduction, To Below Market Rate			1,952	[1],[2]
Interest Rate Reduction, To Interest Only			942	[1],[2],[3]
Below Market Rate			611	[1],[2],[4]
Other			1,059	[1],[2],[5]
Total			5,964	[1],[2]
Commercial and industrial
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only			170	[1],[2]
Interest Rate Reduction, To Below Market Rate			1,771	[1],[2]
Below Market Rate	16	[1],[2],[4]	923	[1],[2],[4]
Other	153	[1],[2],[5]	3,575	[1],[2],[5]
Total	169	[1],[2]	6,439	[1],[2]
Land and construction
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only			367	[1],[6]
Interest Rate Reduction, To Below Market Rate			29,461	[1],[6]
Below Market Rate	425	[1],[2],[4]	15,735	[1],[4],[6]
Other	121	[1],[2],[5]	5,257	[1],[5],[6]
Total	546	[1],[2]	50,820	[1],[6]
Multi-family
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only			2,497	[1],[2]
Below Market Rate			5,819	[1],[2],[4]
Other			1,575	[1],[2],[5]
Total			9,891	[1],[2]
Retail/office
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only			613	[1],[2]
Interest Rate Reduction, To Below Market Rate	214	[1],[2]	2,297	[1],[2]
Interest Rate Reduction, To Interest Only	160	[1],[2],[3]	2,311	[1],[2],[3]
Below Market Rate			1,219	[1],[2],[4]
Other	525	[1],[2],[5]	2,993	[1],[2],[5]
Total	899	[1],[2]	9,433	[1],[2]
Other commercial real estate
Financing Receivable, Impaired [Line Items]
Principal and Interest to Interest Only	540	[1],[2]	1,324	[1],[2]
Interest Rate Reduction, To Below Market Rate	122	[1],[2]	5,315	[1],[2]
Below Market Rate			268	[1],[2],[4]
Other	272	[1],[2],[5]	6,020	[1],[2],[5]
Total	934	[1],[2]	12,927	[1],[2]
Other consumer
Financing Receivable, Impaired [Line Items]
Interest Rate Reduction, To Below Market Rate			285	[1],[2]
Below Market Rate	19	[1],[2],[4]
Other	13	[1],[2],[5]	19	[1],[2],[5]
Total	$ 32	[1],[2]	$ 304	[1],[2]

[1] The unpaid principal balance is inclusive of all partial paydowns and charge-offs since the modification date.

[2] Loans modified in a TDR that were fully paid down, charged-off or foreclosed upon by period end are not reported in this table.

[3] Includes modifications of loan repayment terms from principal and interest to interest only, along with a reduction in the contractual interest rate.

[4] Includes loans modified at below market rates for borrowers with similar risk profiles and having comparable loan terms and conditions. Market rates are determined by reference to internal new loan pricing grids that specify credit spreads based on loan risk rating and term to maturity.

[5] Other modifications primarily include providing for the deferral of interest currently due to the new maturity date of the loan.

[6] Total risk-based capital divided by total risk-weighted assets.