Weighted Average Shares and Net Income Per Share - Calculations of Basic and Diluted Weighted Average Common Shares (Detail) - USD ($)	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Income	$ 13,407,000	$ 11,778,000
Basic:
Weighted average common shares outstanding	18,524,000	18,922,000
Net Income per share	$ 0.72	$ 0.62
Diluted:
Weighted average common shares outstanding	18,524,000	18,922,000
Treasury stock impact of stock options	263,000	180,000
Total common and common equivalent shares	18,787,000	19,102,000
Net Income per share	$ 0.71	$ 0.62