Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 23,175	$ 12,392
Less: earnings allocated to participating securities	216	102
Net income allocated to common shareholders	$ 22,959	$ 12,290
Weighted average number of common shares outstanding - basic (in shares)	50,576	50,586
Share-based plans (in shares)	204	142
Weighted average number of common shares outstanding - diluted (in shares)	50,780	50,728
Basic earnings per share (in usd per share)	$ 0.45	$ 0.24
Diluted earnings per share (in usd per share)	$ 0.45	$ 0.24