Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
Impaired Loans And Leases By Type [Line Items]
With specific reserve required	$ 105,522		$ 173,596
Without a specific reserve	54,833		123,976
Total impaired loans	160,355		297,572
Specific valuation allowance for impaired loans	(29,092)		(44,150)
Carrying amount of impaired loans	131,263		253,422
Average carrying amount of impaired loans	189,919	[1]	304,060	[2]
Loans and troubled debt restructurings on non-accrual status	118,790		224,924
Troubled debt restructurings - accrual	41,565		72,648
Troubled debt restructurings - non-accrual	26,287	[3]	76,378	[3]
Loans past due ninety days or more and still accruing	$ 13,697	[4]	$ 30,697	[4]

[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] Troubled debt restructurings-non-accrual are included in the loans and troubled debt restructurings on non-accrual status line item above.

[4] Includes the guaranteed portion of education loans of $13,697 and $24,641 at March 31, 2013 and 2012, respectively, that were 90+ days past due which continue to accrue interest due to a guarantee provided by government agencies covering approximately 97% of the outstanding balance.