Net Income Per Share - Reconciliation of the numerators and denominators of the basic and diluted net income per share computations (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Net income (numerator):
Net income	$ 4,797	$ 4,541	$ 12,502	$ 13,446
Shares (denominator):
Weighted average number of common shares outstanding used in basic computation	20,038	19,925	20,005	19,892
Common shares issuable upon vesting of restricted stock	114	144	118	140
Common shares issuable upon conversion of preferred shares	10	10	10	10
Shares used in diluted computation	20,162	20,079	20,133	20,042
Net income per common share:
Basic (in dollars per share)	$ 0.24	$ 0.23	$ 0.62	$ 0.68
Diluted (in dollars per share)	$ 0.24	$ 0.23	$ 0.62	$ 0.67