Impaired Loans Segregated by Loans with No Specific Allowance and Loans with Allowance by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Mar. 12, 2012		Mar. 31, 2011
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	$ 54,833		$ 123,976
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	54,833		123,976
With no specific allowance recorded, Average Carrying Amount	86,032	[1]	138,116	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	2,215		2,563
With an allowance recorded, Unpaid Principal Balance	105,522	[3]			173,596	[4]
With an allowance recorded, Associated Allowance	29,092	[3]			44,150	[4]
With an allowance recorded, Carrying Amount	76,430	[3]	129,446		129,446	[4]
With an allowance recorded, Average Carrying Amount	103,887	[1],[3]			165,944	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	3,514	[3]			4,668	[4]
Unpaid Principal Balance, Total	160,355		297,572
Associated Allowance, Total	29,092		44,150
Carrying Amount, Total	131,263		253,422
Average Carrying Amount, Total	189,919	[1]	304,060	[2]
Fiscal Year to Date Interest Income Recognized, Total	5,729		7,231				9,818
Residential
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	11,545		19,845
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	11,545		19,845
With no specific allowance recorded, Average Carrying Amount	12,655	[1]	22,224	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	448		208
With an allowance recorded, Unpaid Principal Balance	25,833	[3]			29,566	[4]
With an allowance recorded, Associated Allowance	7,038	[3]			5,080	[4]
With an allowance recorded, Carrying Amount	18,795	[3]			24,486	[4]
With an allowance recorded, Average Carrying Amount	23,509	[1],[3]			28,070	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	611	[3]			520	[4]
Unpaid Principal Balance, Total	37,378		49,411
Associated Allowance, Total	7,038		5,080
Carrying Amount, Total	30,340		44,331
Average Carrying Amount, Total	36,164	[1]	50,294	[2]
Fiscal Year to Date Interest Income Recognized, Total	1,059		728
Commercial and industrial
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	280		3,389
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	280		3,389
With no specific allowance recorded, Average Carrying Amount	1,020	[1]	6,771	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	75		61
With an allowance recorded, Unpaid Principal Balance	3,480	[3]			7,385	[4]
With an allowance recorded, Associated Allowance	2,508	[3]			5,548	[4]
With an allowance recorded, Carrying Amount	972	[3]			1,837	[4]
With an allowance recorded, Average Carrying Amount	1,556	[1],[3]			6,285	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	78	[3]			260	[4]
Unpaid Principal Balance, Total	3,760		10,774
Associated Allowance, Total	2,508		5,548
Carrying Amount, Total	1,252		5,226
Average Carrying Amount, Total	2,576	[1]	13,056	[2]
Fiscal Year to Date Interest Income Recognized, Total	153		321
Land and construction
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	9,982		34,446
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	9,982		34,446
With no specific allowance recorded, Average Carrying Amount	21,678	[1]	39,601	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	189		581
With an allowance recorded, Unpaid Principal Balance	23,492	[3]			47,545	[4]
With an allowance recorded, Associated Allowance	6,552	[3]			14,543	[4]
With an allowance recorded, Carrying Amount	16,940	[3]			33,002	[4]
With an allowance recorded, Average Carrying Amount	19,024	[1],[3]			47,499	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	659	[3]			886	[4]
Unpaid Principal Balance, Total	33,474		81,991
Associated Allowance, Total	6,552		14,543
Carrying Amount, Total	26,922		67,448
Average Carrying Amount, Total	40,702	[1]	87,100	[2]
Fiscal Year to Date Interest Income Recognized, Total	848		1,467
Multi-family
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	12,217		19,822
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	12,217		19,822
With no specific allowance recorded, Average Carrying Amount	14,826	[1]	21,624	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	400		264
With an allowance recorded, Unpaid Principal Balance	15,448	[3]			27,307	[4]
With an allowance recorded, Associated Allowance	4,261	[3]			7,896	[4]
With an allowance recorded, Carrying Amount	11,187	[3]			19,411	[4]
With an allowance recorded, Average Carrying Amount	13,918	[1],[3]			25,803	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	722	[3]			927	[4]
Unpaid Principal Balance, Total	27,665		47,129
Associated Allowance, Total	4,261		7,896
Carrying Amount, Total	23,404		39,233
Average Carrying Amount, Total	28,744	[1]	47,427	[2]
Fiscal Year to Date Interest Income Recognized, Total	1,122		1,191
Retail/office
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	6,913		21,787
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	6,913		21,787
With no specific allowance recorded, Average Carrying Amount	15,810	[1]	23,577	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	350		816
With an allowance recorded, Unpaid Principal Balance	14,505	[3]			28,954	[4]
With an allowance recorded, Associated Allowance	3,312	[3]			6,672	[4]
With an allowance recorded, Carrying Amount	11,193	[3]			22,282	[4]
With an allowance recorded, Average Carrying Amount	19,553	[1],[3]			27,417	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	519	[3]			858	[4]
Unpaid Principal Balance, Total	21,418		50,741
Associated Allowance, Total	3,312		6,672
Carrying Amount, Total	18,106		44,069
Average Carrying Amount, Total	35,363	[1]	50,994	[2]
Fiscal Year to Date Interest Income Recognized, Total	869		1,674
Other commercial real estate
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	13,365		24,213
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	13,365		24,213
With no specific allowance recorded, Average Carrying Amount	19,378	[1]	23,812	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	691		571
With an allowance recorded, Unpaid Principal Balance	18,618	[3]			24,799	[4]
With an allowance recorded, Associated Allowance	5,057	[3]			4,026	[4]
With an allowance recorded, Carrying Amount	13,561	[3]			20,773	[4]
With an allowance recorded, Average Carrying Amount	19,545	[1],[3]			22,891	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	632	[3]			737	[4]
Unpaid Principal Balance, Total	31,983		49,012
Associated Allowance, Total	5,057		4,026
Carrying Amount, Total	26,926		44,986
Average Carrying Amount, Total	38,923	[1]	46,703	[2]
Fiscal Year to Date Interest Income Recognized, Total	1,323		1,308
Education
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Associated Allowance
With an allowance recorded, Unpaid Principal Balance	424	[3],[5]			762	[4],[6]
With an allowance recorded, Associated Allowance	1	[3],[5]			1	[4],[6]
With an allowance recorded, Carrying Amount	423	[3],[5]			761	[4],[6]
With an allowance recorded, Average Carrying Amount	615	[1],[3],[5]			789	[2],[4],[6]
Unpaid Principal Balance, Total	424	[6]	762	[6]
Associated Allowance, Total	1	[6]	1	[6]
Carrying Amount, Total	423	[6]	761	[6]
Average Carrying Amount, Total	615	[1],[6]	789	[2],[6]
Other consumer
Financing Receivable, Impaired [Line Items]
With no specific allowance recorded, Unpaid Principal Balance	531		474
With no specific allowance recorded, Associated Allowance
With no specific allowance recorded, Carrying Amount	531		474
With no specific allowance recorded, Average Carrying Amount	665	[1]	507	[2]
With no specific allowance recorded, Fiscal Year to Date Interest Income Recognized	62		62
With an allowance recorded, Unpaid Principal Balance	3,722	[3]			7,278	[4]
With an allowance recorded, Associated Allowance	363	[3]			384	[4]
With an allowance recorded, Carrying Amount	3,359	[3]			6,894	[4]
With an allowance recorded, Average Carrying Amount	6,167	[1],[3]			7,190	[2],[4]
Impaired Financing Receivables with Related Allowance Interest Income Accrual Method	293	[3]			480	[4]
Unpaid Principal Balance, Total	4,253		7,752
Associated Allowance, Total	363		384
Carrying Amount, Total	3,890		7,368
Average Carrying Amount, Total	6,832	[1]	7,697	[2]
Fiscal Year to Date Interest Income Recognized, Total	$ 355		$ 542

[1] The average carrying amount of loans in each category is calculated on a trailing 12 month basis.

[2] (1) The average carrying amount of loans in each category is calculated on a trailing 12 month basis.

[3] Includes ratio-based allowance for loan losses of $5.7 million associated with loans totaling $35.9 million at March 31, 2013 for which individual reviews have not been completed but an allowance established based on the ratio of allowance for loan losses to unpaid principal balance for the loans individually reviewed by class of loan.

[4] (2) Includes ratio-based allowance for loan losses of $2.8 million associated with loans totaling $24.6 million at March 31, 2012 for which individual reviews have not been completed but an allowance established based on the ratio of allowance for loan losses to unpaid principal balance for the loans individually reviewed by class of loan.

[5] Excludes the guaranteed portion of education loans 90+ days past due with unpaid principal balance of $13,697 and average carrying amounts totaling $21,249 at March 31, 2013 that are not considered impaired based on a guarantee provided by government agencies.

[6] (3) Excludes the guaranteed portion of education loans 90+ days past due with unpaid principal balance of $24,641 and average carrying amounts totaling $25,520 at March 31, 2012 that are not considered impaired based on a guarantee provided by government agencies.