Summary of Activity for Nonvested Restricted Shares (Detail) - Restricted Stock [Member]	6 Months Ended
	Sep. 30, 2023 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares, Nonvested Restricted Stock March 31, 2023 | shares	219,084
Number of Shares, Granted | shares	97,257
Number of Shares, Vested | shares	(35,958)
Number of Shares, Forfeited | shares	(3,000)
Number of Shares, Nonvested Restricted Stock at September 30, 2023 | shares	277,383
Weighted Average Grant Date Fair Value, Nonvested Restricted Stock March 31, 2023 | $ / shares	$ 96.54
Weighted Average Grant Date Fair Value, Granted | $ / shares	169.62
Weighted Average Grant Date Fair Value, Vested | $ / shares	146.24
Weighted Average Grant Date Fair Value, Forfeited | $ / shares	139.03
Weighted Average Grant Date Fair Value, Nonvested Restricted Stock at September 30, 2023 | $ / shares	$ 125.1