Earnings Per Share - Computation of Basic Earnings and Diluted Earnings Per Share Data (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]
Net income	$ 14,740	$ 9,047	$ 26,623	$ 17,540
Weighted-average basic common shares outstanding	32,918	31,617	32,876	31,670
Stock options	2,243	2,673	2,413	2,609
Denominator for diluted earnings per share-Adjusted weighted-average shares	35,161	34,290	35,289	34,279
Basic	$ 0.45	$ 0.29	$ 0.81	$ 0.55
Diluted	$ 0.42	$ 0.26	$ 0.75	$ 0.51