Net Income Per Common Share - Basic and Diluted Net Income Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share Reconciliation [Abstract]
Income available to common stockholders	$ 44,707	$ 48,192	$ 80,622	$ 90,712
Income available to common stockholders plus assumed exercises of stock options	$ 44,707	$ 48,192	$ 80,622	$ 90,712
Income available to common stockholders - Shares	32,749,752	32,779,227	32,708,563	32,768,102
Dilutive effect of stock options - Shares	668,730	626,696	658,236	639,591
Income available to common stockholders plus assumed exercises of stock options - Shares	33,418,482	33,405,923	33,366,799	33,407,693
Income available to common stockholders - Per Share Amount	$ 1.36	$ 1.47	$ 2.46	$ 2.77
Income available to common stockholders plus assumed exercises of stock options - Per Share Amount	$ 1.34	$ 1.45	$ 2.42	$ 2.72