Earnings Per Common Share - Schedule of Earnings Per Share Basic and Diluted (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator — basic and diluted
Net income	$ 38,945	$ 14,016
Denominator
Weighted average number of common shares outstanding — basic (in shares)	36,700	40,527
Effect of dilutive stock options (in shares)	303	194
Effect of dilutive restricted shares (in shares)	609	524
Weighted average number of common shares outstanding — diluted (in shares)	37,612	41,245
Earnings per common share — basic (in dollars per share)	$ 1.06	$ 0.35
Earnings per common share — diluted (in dollars per share)	$ 1.04	$ 0.34
Stock Options And Restricted Shares
Denominator
Antidilutive stock options and restricted shares (in shares)	613	903