Earnings Per Common Share Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator — basic and diluted
Net income	$ 14,016	$ 30,181
Denominator
Weighted average number of common shares outstanding — basic	40,527	40,506
Effect of dilutive stock options	194	131
Effect of dilutive restricted shares	524	511
Weighted average number of common shares outstanding — diluted	41,245	41,148
Earnings per common share — basic	$ 0.35	$ 0.75
Earnings per common share — diluted	$ 0.34	$ 0.73
Stock Options And Restricted Shares
Denominator
Anti-dilutive securities excluded from computation of earnings per share	903	2,657