Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Number of Shares
Options outstanding at beginning of period	182,665	318,265	444,715
Granted
Exercised	(7,500)	(17,250)
Canceled	(40,521)	(118,350)	(126,450)
Options outstanding at end of period	134,644	182,665	318,265
Weighted Average Exercise Price
Options outstanding at beginning of period	$ 19.11	$ 19.23	$ 19.63
Granted
Exercised	$ 13.47	$ 15.03
Canceled	$ 18.45	$ 20.02	$ 20.64
Options outstanding at end of year	$ 19.82	$ 19.11	$ 19.23