Share-based Compensation - Summary of Non-Vested Stock-Settled SARs Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012
Stock-settled SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Options, Balance, beginning of year	157,410
Non-vested Options, Granted
Non-vested Options, Vested	(75,436)
Non-vested Options, Forfeited, expired, or exercised	(4,882)
Non-vested Options, Balance, end of year	77,092
Weighted Average Grant Date Fair Value, Balance, beginning of year	$ 3.37
Weighted Average Grant Date Fair Value, Granted
Weighted Average Grant Date Fair Value, Vested	$ 3.07
Weighted Average Grant Date Fair Value, Forfeited, expired, or exercised	$ 3.78
Weighted Average Grant Date Fair Value, Balance, end of year	$ 3.64
Cash-settled SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-vested Options, Balance, beginning of year	54,161
Non-vested Options, Granted
Non-vested Options, Vested	(35,416)
Non-vested Options, Forfeited, expired, or exercised	(2,218)
Non-vested Options, Balance, end of year	16,527
Weighted Average Grant Date Fair Value, Balance, beginning of year	$ 2.48
Weighted Average Grant Date Fair Value, Vested	$ 2.33
Weighted Average Grant Date Fair Value, Forfeited, expired, or exercised	$ 2.76
Weighted Average Grant Date Fair Value, Balance, end of year	$ 2.76