Treasury Stock - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024	Nov. 30, 2022
Class of Stock [Line Items]
Number of shares of common stock authorized to repurchase	39,000,000		39,000,000			1,000,000
Treasury stock, value	$ 813,020,000		$ 813,020,000		$ 793,905,000
Treasury stock, shares	38,103,440		38,103,440		38,033,179
Average price per share of common stock	$ 298.49		$ 272.06
Common stock, shares outstanding	17,135,160		17,135,160		17,128,896
Purchase of treasury stock, shares	32,123		70,261
Purchase of treasury stock	$ (9,589,000)	$ (9,418,000)	$ (19,115,000)	$ (27,205,000)
Treasury stock, shares outstanding	38,103,440		38,103,440
Common Stock [Member]
Class of Stock [Line Items]
Purchase of treasury stock, shares	0	0	0	0
Purchase of treasury stock	$ (9,600,000)
1996 Repurchase Program [Member]
Class of Stock [Line Items]
Treasury stock, shares	38,103,440		38,103,440
Common stock equals to percentage of outstanding common stock			69.00%
Average price per share of common stock	$ 311.57		$ 21.34
Purchase of treasury stock, shares	12,023
Purchase of treasury stock	$ (3,700,000)