Note 4 - Long-term Debt (Details Textual)					3 Months Ended
		Apr. 21, 2021 USD ($)	Apr. 20, 2021 USD ($) $ / shares shares	Aug. 16, 2018 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Repayments of Lines of Credit					$ 1,250,000	$ (0)
Subsequent Event [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares			10,900,000
Subsequent Event [Member] | Series A Preferred Stock [Member] | New Notes Trustee [Member]
Stock Issued During Period, Shares, New Issues (in shares) | shares			1
Preferred Stock, Liquidation Preference, Value			$ 1.00
Preferred Stock, Convertible, Percentage of Debt Instrument Converted			75.00%
Convertible Preferred Stock, Conversion Price (in dollars per share) | $ / shares			$ 1.00
Subsequent Event [Member] | Exchange Offer [Member]
Debt Conversion, Original Debt, Amount			$ 113,500,000
Line of Credit [Member] | Revolving Credit Facility [Member]
Long-term Debt, Gross	[1]				21,250,000		$ 22,500,000
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member]
Debt Instrument, Covenant, Minimum Excess Borrowing Availability for Five Consecutive Business Days				$ 6,250,000
Debt Instrument, Covenant, Minimum Excess Borrowing Availability on Any Given Business Day				5,000,000.0
Line of Credit Facility, Maximum Borrowing Capacity				50,000,000.0
Debt Instrument, Covenant, Maximum Borrowing Base Percentage of Net Orderly Liquidation Value, Multi-client Data Library				$ 28,500,000
Long-term Line of Credit, Total					21,300,000
Line of Credit Facility, Remaining Borrowing Capacity					5,300,000
Debt Instrument, Covenant, Minimum Fixed Cover Charge Ratio				1.1
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | Subsidiary Borrowers [Member]
Debt Instrument, Percentage of Ownership Interest in Subsidiaries Subject to First Priority Security Interest				100.00%
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | ION International Holdings L.P. [Member]
Debt Instrument, Percentage of Ownership Interest in Subsidiaries Subject to First Priority Security Interest				65.00%
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | GX Geoscience Corporation, S. De R.L. De C.V. [Member]
Line of Credit Facility, Maximum Borrowing Capacity					5,000,000.0
Debt Instrument, Covenant, Borrowing Base, Maximum Eligible Billed Receivables				$ 5,000,000.0
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | Maximum [Member] | Base Rate [Member]
Debt Instrument, Basis Spread on Variable Rate				3.00%
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate				4.00%
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | Minimum [Member] | Base Rate [Member]
Debt Instrument, Basis Spread on Variable Rate				2.00%
Line of Credit [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate				3.00%
Line of Credit [Member] | Subsequent Event [Member] | Revolving Credit Facility [Member] | PNC Bank, National Association [Member]
Line of Credit Facility, Remaining Borrowing Capacity		$ 6,250,000
Repayments of Lines of Credit		$ 1,500,000
Second Lien Notes [Member] | Senior Notes [Member]
Long-term Debt, Gross					$ 120,569,000		$ 120,569,000
Second Lien Notes [Member] | Senior Notes [Member] | Subsequent Event [Member]
Long-term Debt, Gross			120,600,000
Long-term Debt, Total			$ 7,100,000
Debt Instrument, Interest Rate, Stated Percentage			9.125%
New Second Lien Notes [Member] | Senior Notes [Member] | Subsequent Event [Member]
Debt Instrument, Interest Rate, Stated Percentage			8.00%
Debt Instrument, Convertible, Number of Shares to be Issued Per $1000 (in shares) | shares			333
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares			$ 3.00
Debt Instrument, Convertible, Number of Equity Instruments			38,700,000
Debt Instrument, Convertible, Number of Additional Equity Instruments (in shares) | shares			6,500,000
Debt Instrument, Convertible, Optional Conversion Period After Issue Date (Month)			18 months
Debt Instrument, Convertible, Threshold Trading Days			20
Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger			175.00%
Debt Instrument, Covenant, Sale of Certain Assets, Percentage of Proceeds to Repurchase Debt			100.00%
New Second Lien Notes [Member] | Senior Notes [Member] | Subsequent Event [Member] | Debt Instrument, Redemption, Period One [Member]
Debt Instrument, Redemption Price, Percentage			100.00%
New Second Lien Notes [Member] | Senior Notes [Member] | Subsequent Event [Member] | Debt Instrument, Redemption, Period Two [Member]
Debt Instrument, Redemption Price, Percentage			100.00%
New Second Lien Notes [Member] | Senior Notes [Member] | Subsequent Event [Member] | Debt Instrument, Redemption, Period Three [Member]
Debt Instrument, Redemption Price, Percentage			101.00%

[1] The maturity of the revolving credit facility will accelerate if the Company is unable to repay or extend the maturity of the Existing Second Lien Notes (see detailed discussion below in "Revolving Credit Facility").