Share-based Compensation - Summary of Non-Vested Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Stock Option Activity [Line Items]
Non-vested stock Options, Balance, beginning of year	412,943	447,693	518,275
Non-vested stock Options, Granted			62,475
Non-vested stock Options, Forfeited, expired, or exercised	16,038	20,750	116,649
Non-vested stock Options, Balance, end of year	367,906	412,943	447,693
Weighted Average Exercise Price, Balance, beginning of year	$ 13.74	$ 13.61	$ 13.85
Weighted Average Grant Date Fair Value, Granted			$ 11.30
Weighted Average Grant Date Fair Value, Forfeited, expired, or exercised	$ 16.86	$ 15.81	$ 14.46
Weighted Average Exercise Price, Balance, end of year	$ 14.15	$ 13.74	$ 13.61
Non Vested Options [Member]
Schedule Of Stock Option Activity [Line Items]
Non-vested stock Options, Balance, beginning of year	117,775
Non-vested stock Options, Granted
Non-vested stock Options, Vested	(61,889)
Non-vested stock Options, Forfeited, expired, or exercised
Non-vested stock Options, Balance, end of year	55,886
Weighted Average Exercise Price, Balance, beginning of year	$ 3.32
Weighted Average Grant Date Fair Value, Granted
Weighted Average Grant Date Fair Value, Vested	$ 3.08
Weighted Average Grant Date Fair Value, Forfeited, expired, or exercised
Weighted Average Exercise Price, Balance, end of year	$ 3.58