Earnings Per Share - Computation of Basic and Diluted (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Income (Loss)	$ 5,583	$ 6,417	$ 12,560	$ 4,831
Denominator:
Denominator for basic earnings per share - Weighted-average shares	17,107,727	16,309,053	17,090,093	16,270,955
Effect of dilutive stock options (in shares)	491,000	555,000	546,000	572,000
Denominator for diluted earnings per share - Adjusted weighted-average shares and assumed conversions	17,599,481	16,864,166	17,636,440	16,842,768
Basic income (loss) per share (in dollars per share)	$ 0.33	$ 0.40	$ 0.73	$ 0.29
Diluted income (loss) per share (in dollars per share)	$ 0.32	$ 0.38	$ 0.71	$ 0.28