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	Jun. 30, 2012 Investment
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	20
Number of investment positions in continuous loss position more than twelve months	3
Number of investment positions in continuous loss position	23
Fair value of securities in continuous loss position more than twelve months	$ 16,211
Fair value of securities in continuous loss position more than twelve months	1,600
Fair value of securities in continuous loss position	17,811
Gross unrealized losses of securities in continuous loss position less than twelve months	81
Gross unrealized losses of securities in continuous loss position more than twelve months	74
Gross unrealized losses of securities in continuous loss position	155
Agency Collateralized Mortgage Obligations
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	5
Fair value of securities in continuous loss position more than twelve months	4,747
Gross unrealized losses of securities in continuous loss position less than twelve months	6
Agency notes and bonds
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	10
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	7,952
Fair value of securities in continuous loss position more than twelve months	1,043
Gross unrealized losses of securities in continuous loss position less than twelve months	47
Gross unrealized losses of securities in continuous loss position more than twelve months	1
Agency mortgage-backed securities
Investments, Unrealized Loss Position [Line Items]
Number of investment positions in continuous loss position less than twelve months	3
Fair value of securities in continuous loss position more than twelve months	3,099
Gross unrealized losses of securities in continuous loss position less than twelve months	17
Municipal Notes
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 more than twelve months	413
Gross unrealized losses of securities in continuous loss position less than twelve months	11
Collateralized Mortgage Obligations Issued By Private Enterprise
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	194
Gross unrealized losses of securities in continuous loss position more than twelve months	49
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	363
Gross unrealized losses of securities in continuous loss position more than twelve months	$ 24