Long-Term Debt Payable to Banks - Additional Information (Detail)	6 Months Ended
	Sep. 30, 2015 USD ($)
Line Of Credit Facility [Line Items]
Revolving credit facility	$ 0
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Unused borrowing commitment fee	0.125%
Revolving credit facility expiration date	Aug. 26, 2018
Line of Credit Facility, Commitment Fee Percentage	0.125%
Minimum borrowing capacity after dividend payment	$ 5,000,000
Outstanding letters of credit	702,000
Revolving Credit Facility | Maximum
Line Of Credit Facility [Line Items]
Revolving credit facility	$ 8,000,000
Revolving Credit Facility | Unsecured Debt
Line Of Credit Facility [Line Items]
Senior credit facility period	5 years
Senior credit facility	$ 20,000,000
Line of credit, maximum borrowing capacity	$ 35,000,000
Revolving Line of credit Description	accordion feature that may increase the amount to 2.5 times EBITDA
Option to convert Revolving Credit Facility, description	The Company has the option, subject to bank approval, during the five-year term of the Revolving Credit Facility, to convert the Facility to a secured credit facility which increases the borrowing limit to 3.5 times EBITDA (as defined in the Facility) up to a maximum of $35,000. As of September 30, 2015, the Company has not exercised this option.
Line of credit, remaining borrowing capacity	$ 19,298,000