Unpaid Principal Balance of Loans by Risk Category (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	$ 1,763,196		$ 2,188,083
Pass
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	1,519,665	[1]	1,740,542	[1]
Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	33,363		56,762
Total pass and special mention rated loans
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	1,533,028		1,797,304
Substandard, Excluding TDR Accrual
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	49,813		93,207
Troubled Debt Restructurings accrual
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	41,565		72,648
Non-Accrual
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	118,790		224,924
Total impaired loans
Financing Receivable, Recorded Investment [Line Items]
Total Unpaid Principal Balance	$ 160,355		$ 297,572

[1] Includes all accrual residential and consumer loans as these loans are not individually rated.