Summary of Status and Changes in Stock Option Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Shares
Options outstanding, Beginning balance	817,815
Options granted	58,000
Options exercised	67,916	2,832	0
Options forfeited and expired	19,540
Options outstanding, Ending balance	788,359	817,815
Options exercisable at year end	770,959
Weighted Average Exercise Price
Options Outstanding, Weighted Average Exercise Price, Beginning balance	$ 11.09
Options Granted, Weighted Average Exercise Price	$ 11.37
Options Exercised, Weighted Average Exercise Price	$ 8.12
Options Forfeited/expired, Weighted Average Exercise Price	$ 14.76
Options Outstanding, Weighted Average Exercise Price, Ending balance	$ 11.27	$ 11.09
Options exercisable, Weighted Average Exercise Price	$ 11.31
Weighted- Average Remaining Contractual Life (in years)
Options Outstanding, Weighted-Average Remaining Contractual Life	7 years 3 months 18 days
Aggregate Intrinsic Value
Options Outstanding, Aggregate Intrinsic Value	$ 1,753