Weighted Average Shares and Net Income Per Share - Calculations of Basic and Diluted Weighted Average Common Shares (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Income	$ 16,843,000	$ 8,302,000
Basic:
Weighted average common shares outstanding	17,897,000	17,983,000
Net Income per share	$ 0.94	$ 0.46
Diluted:
Weighted average common shares outstanding	17,897,000	17,983,000
Treasury stock impact of stock options	323,000	131,000
Total common and common equivalent shares	18,220,000	18,114,000
Net Income per share	$ 0.92	$ 0.46