Disclosures about Fair Value of Assets and Liabilities - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Fair value adjustments on impaired loans	$ 1,300,000		$ 1,900,000
Increase in carrying amount of mortgage servicing rights	$ 208,000	$ 369,000