Summary of Activity in Allowance for Loan Losses (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance at beginning of year	$ 111,215	$ 150,122	$ 179,644
Provision	7,733	33,887	50,325
Charge-offs	(49,353)	(82,562)	(88,886)
Recoveries	10,220	9,768	9,039
Allowance at end of year	$ 79,815	$ 111,215	$ 150,122