Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Taxes
Unrecognized tax benefits netted against certain noncurrent deferred tax assets	$ 861,000	$ 580,000
Unrecognized tax benefits that, if recognized, would affect effective tax rate	840,000	609,000
Gross unrecognized tax benefits
Gross unrecognized tax benefits at beginning of year	687,000	586,000	$ 426,000
Increases for tax positions taken in prior years	101,000	2,000	62,000
Increases for tax positions taken in the current year	180,000	116,000	122,000
Lapse in statute of limitations	(16,000)	(17,000)	(24,000)
Gross unrecognized tax benefits at March 31	$ 952,000	$ 687,000	$ 586,000