Summary of Activity for Company's Non-vested Options (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Number of Shares
Non-vested options - beginning	79,640
Granted	20,633
Vested	(42,147)
Forfeited or expired	(3,710)
Non-vested options - ending	54,416
Weighted Average Grant-Date Fair Value
Non-vested options - beginning	$ 6.33
Granted	$ 7.85
Vested	$ 5.44
Forfeited or expired	$ 6.80
Non-vested options - ending	$ 7.56