Stock-Based Compensation and Stock Options - Stock Options Outstanding and Exercisable (Detail) - $ / shares	9 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Mar. 31, 2018
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Outstanding Options	1,099,514	990,064	1,058,411	1,121,527	1,053,307	1,064,439
Weighted Average Remaining Contractual Life	3 years 5 months 8 days
Outstanding Options – Weighted Average Exercise Price	$ 53.66	$ 49.84	$ 45.17	$ 44.08	$ 41.81	$ 39.45
Exercisable Options – Number of Exercisable Options	381,646
Exercisable Options – Weighted Average Exercise Price	$ 38.79
Range of Exercise Price, $20.08 to $43.32 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	20.08
Range of Exercise Price, upper limit	$ 43.32
Number of Outstanding Options	298,294
Weighted Average Remaining Contractual Life	2 years 3 months 10 days
Outstanding Options – Weighted Average Exercise Price	$ 31.58
Exercisable Options – Number of Exercisable Options	230,010
Exercisable Options – Weighted Average Exercise Price	$ 30.74
Range of Exercise Price, $43.33 to $57.75 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	43.33
Range of Exercise Price, upper limit	$ 57.75
Number of Outstanding Options	391,449
Weighted Average Remaining Contractual Life	3 years 2 months 8 days
Outstanding Options – Weighted Average Exercise Price	$ 52.58
Exercisable Options – Number of Exercisable Options	146,627
Exercisable Options – Weighted Average Exercise Price	$ 50.72
Range of Exercise Price, $57.76 to $77.93 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	57.76
Range of Exercise Price, upper limit	$ 77.93
Number of Outstanding Options	359,321
Weighted Average Remaining Contractual Life	4 years 3 months 14 days
Outstanding Options – Weighted Average Exercise Price	$ 68.42
Exercisable Options – Number of Exercisable Options	5,009
Exercisable Options – Weighted Average Exercise Price	$ 59.32
Range of Exercise Price, $77.94 to $87.49 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise Price, lower limit	77.94
Range of Exercise Price, upper limit	$ 87.49
Number of Outstanding Options	50,450
Weighted Average Remaining Contractual Life	6 years 1 month 2 days
Outstanding Options – Weighted Average Exercise Price	$ 87.49
Exercisable Options – Number of Exercisable Options	0
Exercisable Options – Weighted Average Exercise Price	$ 0