Stockholders' Equity - Computation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator:
Net income (loss) available to common shareholders	$ 8,913	$ (15,298)	$ 36,368	$ 19,495
Denominator:
Basic weighted average shares outstanding	31,606,264	33,660,212	32,538,832	33,772,710
Effect of dilutive securities:
SARs and options	237,602		268,016	566,190
Restricted stock	164,915		159,469	168,010
Diluted weighted average shares outstanding	32,008,781	33,660,212	32,966,317	34,506,910
Basic earnings (loss) per share	$ 0.28	$ (0.45)	$ 1.12	$ 0.58
Diluted earnings (loss) per share	$ 0.28	$ (0.45)	$ 1.10	$ 0.56