Investment Securities Available for Sale with Gross Unrealized Losses Aggregated by Investment Category and Length of Time Individual Investment Securities Have Been in Continuous Position (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 Investment
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	31
Number of investment positions in continuous loss position more than twelve months	1
Number of investment positions in continuous loss position	32
Fair value of securities in continuous loss position less than twelve months	$ 20,247
Fair value of securities in continuous loss position more than twelve months	389
Fair value of securities in continuous loss position	20,636
Gross unrealized losses of securities in continuous loss position less than twelve months	251
Gross unrealized losses of securities in continuous loss position more than twelve months	12
Gross unrealized losses of securities in continuous loss position	263
Agency notes and bonds
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	2
Fair value of securities in continuous loss position less than twelve months	1,967
Gross unrealized losses of securities in continuous loss position less than twelve months	4
Agency CMO
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	4
Fair value of securities in continuous loss position less than twelve months	4,217
Gross unrealized losses of securities in continuous loss position less than twelve months	4
Agency mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	4
Fair value of securities in continuous loss position less than twelve months	4,813
Gross unrealized losses of securities in continuous loss position less than twelve months	22
Municipal Obligations
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	21
Fair value of securities in continuous loss position less than twelve months	9,250
Gross unrealized losses of securities in continuous loss position less than twelve months	221
Mutual funds
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position more than twelve months	1
Fair value of securities in continuous loss position more than twelve months	389
Gross unrealized losses of securities in continuous loss position more than twelve months	$ 12