Income Taxes - Reconciliation of income tax provision computed at the U.S. federal statutory tax rates to income tax expense (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes at U.S. statutory rates	$ 13,274	$ 11,399	$ 9,729
State income taxes, net of federal tax benefit	858	675	589
Permanent differences	1	(23)	(29)
Other	(28)	(51)	56
Total provision for income taxes	$ 14,105	$ 12,000	$ 10,345