Long-Term Debt and Notes Payable - Additional Information (Detail) | 3 Months Ended | 12 Months Ended | | |
Apr. 30, 2017USD ($) | Apr. 30, 2016USD ($) | Jan. 31, 2017USD ($) | Nov. 30, 2016USD ($) | Aug. 22, 2014USD ($) |
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 | | | |