Net Income Per Share - Reconciliation of the numerators and denominators of the basic and diluted net income per share computations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income (numerator):
Net income (in dollars)	$ 4,899	$ 4,502	$ 11,493	$ 10,259
Shares (denominator)
Weighted average number of common shares outstanding used in basic computation	20,234	20,126	20,208	20,100
Common shares issuable upon vesting of restricted stock	133	110	137	112
Common shares issuable upon conversion of preferred shares	10	10	10	10
Shares used in diluted computation	20,377	20,246	20,355	20,222
Net income per common share:
Basic (in dollars per share)	$ 0.24	$ 0.22	$ 0.57	$ 0.51
Diluted (in dollars per share)	$ 0.24	$ 0.22	$ 0.56	$ 0.51