Stockholders' Equity - Basic and Diluted Net Income Per Common Shares (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
Equity [Abstract]
Net income	$ 5,762	$ 8,048	$ 19,515	$ 24,957
Weighted average shares of common stock outstanding	21,629,289	21,973,473	21,653,692	22,069,785
Dilutive effect of restricted stock and RSUs	289,949	426,461	262,371	464,342
Weighted average shares of common stock and common stock equivalents	21,919,238	22,399,934	21,916,063	22,534,127
Basic	$ 0.27	$ 0.37	$ 0.90	$ 1.13
Diluted	$ 0.26	$ 0.36	$ 0.89	$ 1.11