Combined Stock Options and Stock Appreciation Rights Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Number of Shares
Options and SAR's outstanding at beginning of year	2,108,003	1,625,253
Granted	204,000	679,000
Cancelled	(212,749)	(74,187)
Expired	(7,714)	(875)
Exercised	(297,855)	(121,188)
Options and SAR's outstanding at end of year	1,793,685	2,108,003
Weighted average exercise price
Options and SAR's outstanding at beginning of year	$ 7.26	$ 6.92
Granted	$ 12.06	$ 6.98
Cancelled	$ 6.58	$ 6.41
Expired	$ 1.68	$ 3.04
Exercised	$ 4.74	$ 1.60
Options and SAR's outstanding at end of year	$ 8.30	$ 7.26