Premises, Equipment and Lease Commitments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2013 Facility	Mar. 31, 2012	Mar. 31, 2011
Schedule of Operating Leases [Line Items]
Number of facilities leased	21
Operating lease expiration year	2030
Land and building lease rental expense	$ 1.9	$ 2.2	$ 2.4
Minimum
Schedule of Operating Leases [Line Items]
Non-cancelable operating lease remaining term	1 year