Long-Term Debt and Notes Payable - Additional Information (Detail)	3 Months Ended		12 Months Ended
	Apr. 30, 2017 USD ($)	Apr. 30, 2016 USD ($)	Jan. 31, 2017 USD ($)	Nov. 30, 2016 USD ($)	Aug. 22, 2014 USD ($)
London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Interest rate of borrowings	3.00%
Seamap Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowings under the revolving credit facility					$ 15,000,000
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Borrowings under the revolving credit facility			$ 20,000,000	$ 10,000,000
Maturity of the credit agreement			Aug. 31, 2017
Available borrowings under the revolving credit facility to secure letters of credit			$ 10,000,000
Credit Agreement [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Commitment fee on the unused portion of the Credit Agreement			0.375%
Credit Agreement [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Commitment fee on the unused portion of the Credit Agreement			0.50%
Credit Agreement [Member] | ABR [Member]
Line of Credit Facility [Line Items]
Credit Agreement basis points			2.50%
Credit Agreement [Member] | ABR [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Leverage ratio	1.50
Credit Agreement [Member] | ABR [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Leverage ratio	2.50
Credit Agreement [Member] | Eurodollar [Member]
Line of Credit Facility [Line Items]
Credit Agreement basis points			3.50%
Credit Agreement [Member] | Eurodollar [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Leverage ratio	2.50
Credit Agreement [Member] | Eurodollar [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Leverage ratio	3.50
Term Loan [Member]
Line of Credit Facility [Line Items]
Carrying value of debt					10,000,000
Frequency of periodic payments	The term loan portion of the Seamap Credit Facility provided for eleven quarterly principal payments of $800,000 and a final payment of the remaining $1.2 million on or before August 22, 2017.
Maturity period	Aug. 22, 2017
Principal payment of term loan portion	$ 800,000
Final payment of term portion	1,200,000
Term Loan [Member] | Seamap Singapore [Member]
Line of Credit Facility [Line Items]
Borrowings under the revolving credit facility	$ 3,000,000
Term Loan [Member] | Minimum [Member] | Seamap Singapore [Member]
Line of Credit Facility [Line Items]
Borrowing period	1 month
Term Loan [Member] | Maximum [Member] | Seamap Singapore [Member]
Line of Credit Facility [Line Items]
Borrowing period	3 months
Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Credit Agreement basis points	2.75%
Singapore Credit Facility Bankers Guarantees [Member]
Line of Credit Facility [Line Items]
Carrying value of debt					2,000,000
Revolving Credit Facility [Member] | Term Loan [Member]
Line of Credit Facility [Line Items]
Borrowings under the revolving credit facility					$ 3,000,000
Seamap Credit Facility [Member] | Credit Agreement [Member]
Line of Credit Facility [Line Items]
Average borrowings under the revolving credit facility	$ 3,300,000	$ 19,300,000