Earnings Per Share - Basic and diluted earnings per share (Details) (USD $)	3 Months Ended		6 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Share [Abstract]
Numerator for earnings per share - net income	$ 4,316,552	$ 5,150,138	$ 10,017,045	$ 10,557,594
Denominator:
Denominator for basic earnings per share - weighted average shares	12,092,246	11,963,596	12,078,703	11,956,362
Effect of dilutive securities:
Stock options and other share awards	222,995	218,469	194,879	232,939
Denominator for diluted earnings per share	12,315,241	12,182,065	12,273,582	12,189,301
Earnings per share:
Basic (in dollars per share)	$ 0.36	$ 0.43	$ 0.83	$ 0.88
Diluted (in dollars per share)	$ 0.35	$ 0.42	$ 0.82	$ 0.87