Note 7 - Debt (Details Textual) - USD ($) $ in Thousands			3 Months Ended			6 Months Ended
	Oct. 23, 2020	Sep. 23, 2020	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2020	Aug. 31, 2015
Letters of Credit Outstanding, Amount			$ 29,500		$ 29,500	$ 29,500
Repayments of Lines of Credit						482,996	$ 803,397
Transport Financial Services [Member] | Discontinued Operations, Disposed of by Sale [Member]
Discontinued Operation, Amount of Continuing Cash Flows after Disposal				$ 35,600	$ (35,600)
Interest Rate Swap [Member]
Derivative, Fixed Interest Rate									4.20%
Variable Rate Note [Member]
Debt Instrument, Face Amount									$ 28,000
Lenders [Member]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.25%
Percent of Eligible Accounts Receivable	87.50%
Percent of Appraised Net Orderly Liquidation, Value of Eligible Revenue Equipment	85.00%
Percent of Net Book Value of Eligible Revenue Equipment	100.00%
Line of Credit Facility, Availability as Percentage of Revolver Commitment	40.90%
Line of Credit Facility, Revolver Commitment, Amount	$ 45,000
Line of Credit Facility, Maximum Commitment Value	$ 10,400
Percent of Appraised Fair Market Value of Eligible Real Estate	80.00%
Long-term Line of Credit, Total			10,000			10,000
Letters of Credit Outstanding, Amount			29,500			29,500
Line of Credit Facility, Remaining Borrowing Capacity			70,500			70,500
Fixed Charge Coverage Requirement						0	$ 0
Debt, Secured with a Cross Default Feature			6,100			6,100
Lenders [Member] | Federal Funds Rate [Member] | Base Rate Loans [Member]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Lenders [Member] | London Interbank Offered Rate (LIBOR) [Member] | Base Rate Loans [Member]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Lenders [Member] | Applicable Margin [Member] | Base Rate Loans [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.25%
Lenders [Member] | Applicable Margin [Member] | Base Rate Loans [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	0.75%
Lenders [Member] | Applicable Margin [Member] | LIBOR Loans [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.25%
Lenders [Member] | Applicable Margin [Member] | LIBOR Loans [Member] | Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate	1.75%
Lenders [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 110,000
Line of Credit Facility, Maximum Increase in Borrowing Capacity	50,000
Lenders [Member] | Revolving Credit Facility [Member] | LIBOR Loans [Member]
Long-term Line of Credit, Total			10,000			10,000
Lenders [Member] | Letter of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	105,000
Line of Credit Facility, Borrowing Capacity, Percentage of Aggregate Commitments	$ 10,000
Lenders [Member] | Swing Line Sub Facility [Member]
Percent of Aggregate Commitments under Credit Facility	10.00%
TBK Bank [Member] | Draw Note [Member]
Line of Credit Facility, Remaining Borrowing Capacity			40,400			40,400
Debt Instrument, Face Amount								$ 45,000
Debt Instrument, Collateral Amount		$ 60,000
Repayments of Lines of Credit			31,000
Long-term Debt, Total			$ 4,600			$ 4,600
TBK Bank [Member] | London Interbank Offered Rate (LIBOR) [Member] | Draw Note [Member]
Debt Instrument, Basis Spread on Variable Rate		1.50%
TBK Bank [Member] | London Interbank Offered Rate (LIBOR) [Member] | Draw Note [Member] | Minimum [Member]
Debt Instrument, Basis Spread on Variable Rate		0.25%