Earnings Per Share - Computation of Earnings Per Share (Detail) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income	$ 7,430	$ 23,061	$ 23,551	$ 45,787
Average number of common shares outstanding (in shares)	29,754	30,458	30,074	30,441
Effect of dilutive stock options and restricted stock (in shares)	129	185	129	209
Average number of common shares outstanding used to calculate diluted earnings per share (in shares)	29,883	30,643	30,203	30,650
Options excluded from diluted earnings per share because the effect of these options was antidilutive (in shares)	0	0	0	0