Stock Options - Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Number of Shares
Outstanding Beginning Balance	1,026,588	978,688	929,850
Options granted	190,500	222,100	224,000
Options exercised	(437,937)	0	(79,937)
Options forfeited	(77,150)	(174,200)	(95,225)
Outstanding Ending Balance	702,001	1,026,588	978,688
Exercisable at end of period	245,750	568,985	530,262
Available for grant at December 31	111,343	78,350	230,950
Weighted-Average Exercise Price
Beginning Balance	$ 18.69	$ 20.89	$ 20.65
Options granted	$ 22.42	$ 9.81	$ 21.61
Options exercised	$ 20.05	$ 0.00	$ 19.42
Options forfeited	$ 22.35	$ 19.70	$ 21.55
Ending Balance	$ 18.45	$ 18.69	$ 20.89
Exercisable at end of period	$ 19.74	$ 21.46	$ 21.52