Stock-Based Compensation - LTIP NQSOs (Details) - Stock Incentive Plan 2015 - LTIP NQSOs - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Number of Shares
Number of shares outstanding beginning of period (in shares)	302,939	361,383	397,340
Forfeited (in shares)			(35,957)
Exercised (in shares)	(107,197)	(58,444)
Number of shares outstanding end of period (in shares)	195,742	302,939	361,383	397,340
Weighted- Average Grant-Date Fair Value
Outstanding at the beginning of the period (in dollars per share)	$ 66.02	$ 65.35	$ 65.70
Forfeited (in dollars per share)			(69.29)
Exercised (in dollars per share)	(63.20)	(61.86)
Outstanding at the end of the period (in dollars per share)	$ 67.56	$ 66.02	$ 65.35	$ 65.70
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted- Average Remaining Contractual Term (Years)	3 years 7 months 6 days	5 years	6 years 2 months 12 days	7 years 1 month 6 days
Aggregate Intrinsic Value	$ 51,452	$ 20,594	$ 29,504	$ 9,666