Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Allowance for doubtful accounts:
Provision for doubtful accounts	$ 421	$ 260	$ 94
Allowance for Doubtful Accounts
Allowance for doubtful accounts:
Balance at beginning of period	13	8	7
Provision for doubtful accounts	421	260	94
Write-off of uncollectible accounts receivable	(407)	(255)	(93)
Balance at end of year	$ 27	$ 13	$ 8