Employee Benefit Plans - Employee Incentive Programs (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Profit Sharing Plan
Employee incentive programs
Employer contribution under plan (in dollars)	$ 0	$ 0	$ 0
401 (k) Plan
Employee incentive programs
Employer contribution under plan (in dollars)	$ 1,317,000	$ 1,185,000	$ 1,067,000
Employer matching contribution (as a percent)	50.00%
Vesting period of employer matching contributions	3 years