Schedule of Calculation of Numerator and Denominator in Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic and dilutive numerator:
Net income (loss)	$ 13,370	$ (4,716)	$ 23,208	$ (13,005)
Denominator:
Weighted-average common shares outstanding - basic (in thousands)	28,163	27,936	28,149	27,925
Net effect of dilutive securities:
Stock options and restricted stock	665		623
Weighted-average common shares outstanding - diluted (in thousands)	28,828	27,936	28,772	27,925
Net income (loss) per common share (basic)	$ 0.47	$ (0.17)	$ 0.82	$ (0.47)
Net income (loss) per common share (diluted)	$ 0.46	$ (0.17)	$ 0.81	$ (0.47)