Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 103,469	$ 86,270	$ 55,054
Less: non-forfeitable dividends on restricted stock	3	4	10
Net income available to common shareholders	$ 103,466	$ 86,266	$ 55,044
Weighted average common shares outstanding (in shares)	72,099,755	72,607,321	72,479,807
Weighted average potential dilutive common shares (in shares)	1,376,008	1,812,789	392,381
Weighted average common shares outstanding-assuming dilution (in shares)	73,475,763	74,420,110	72,872,188
Net income per common share - basic (in dollar per share)	$ 1.44	$ 1.19	$ 0.76
Net income per common share - diluted (in dollar per share)	$ 1.41	$ 1.16	$ 0.76