Investment Securities Available for Sale - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Investments Debt And Equity Securities [Abstract]
Realized gains on the sale of investment securities available for sale	$ 42,000	$ 226,000	$ 42,000	$ 226,000
Investment securities available for sale, callable, Amortized cost	55,000,000		55,000,000
Investment securities available for sale, callable, Estimated market	$ 44,600,000		$ 44,600,000
Floating-rate securities, purchased period			May 1998 to September 1998
Floating-rate debt securities, fixed interest rate period			Over 90-day LIBOR
Principal maturity year			2028 or prior if called by the issuer