Computation of Basic and Diluted Net (Loss) Income Per Common Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Net (loss) income	$ (1,711)	$ 2,745	$ (1,193)	$ 13,536
Adjustment for interest expense on convertible notes		96		304
Net (loss) income, as adjusted	$ (1,711)	$ 2,841	$ (1,193)	$ 13,840
Denominator:
Weighted average number of shares of common stock outstanding	6,960,967	6,877,915	6,943,208	6,863,564
Weighted average effect of assumed conversion of convertible notes		427,396		427,912
Weighted average effect of dilutive stock options and other stock compensation		128,611		155,360
Weighted average number of shares of common stock outstanding, as adjusted	6,960,967	7,433,922	6,943,208	7,446,836
Net (loss) income per common share:
Net (loss) income per common share - Basic	$ (0.25)	$ 0.40	$ (0.17)	$ 1.97
Net (loss) income per common share - Diluted	$ (0.25)	$ 0.38	$ (0.17)	$ 1.86