Earnings Per Share - Computation of Basic and Diluted (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Numerator:
Income (Loss)	$ 6,976	$ (1,586)
Denominator:
Denominator for basic earnings per share - Weighted-average shares	17,072,459	16,232,856
Effect of dilutive stock options (in shares)	601,000
Denominator for diluted earnings per share - Adjusted weighted-average shares and assumed conversions	17,673,399	16,232,856
Basic income (loss) per share (in dollars per share)	$ 0.41	$ (0.10)
Diluted income (loss) per share (in dollars per share)	$ 0.39	$ (0.10)