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, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income available to common shareholders	$ 12,392	$ 15,626
Less: earnings allocated to participating securities	102	141
Net income allocated to common shareholders	$ 12,290	$ 15,485
Weighted average number of common shares outstanding - basic (in shares)	50,586	50,275
Share-based plans (in shares)	142	167
Weighted average number of common shares outstanding - diluted (in shares)	50,728	50,442
Basic earnings per share (in usd per share)	$ 0.24	$ 0.31
Diluted earnings per share (in usd per share)	$ 0.24	$ 0.31