Summary of Significant Accounting Policies - Net Loss Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator:
Net income	$ 11,229	$ 9,847	$ 8,161	$ 8,522
Denominator:
Weighted average shares outstanding for basic net income per common share (in shares)	9,148	9,323	9,245	9,316
Effect of dilutive stock options (in shares)	89	74	100	77
Adjusted weighted average share outstanding for diluted net income per common share (in shares)	9,237	9,397	9,345	9,393
Basic net income per common share (in dollars per share)	$ 1.23	$ 1.06	$ 0.88	$ 0.91
Diluted net income per common share (in dollars per share)	$ 1.22	$ 1.05	$ 0.87	$ 0.91