Note 7 - Long-term Debt (Details Textual) - USD ($) | 1 Months Ended | | | | |
Feb. 28, 2015 | Mar. 31, 2018 | Dec. 31, 2017 | Mar. 31, 2017 | Dec. 31, 2016 |
Revolving Credit Facility [Member] | | | | | |
Line of Credit Facility, Maximum Borrowing Capacity | $ 170,000,000 | | | | |
Line Of Credit Facility Additional Borrowing Capacity | 80,000,000 | | | | |
Line of Credit Facility, Additional Borrowing Capacity, Incremental Amount | $ 20,000,000 | | | | |
Debt Instrument, Term | 5 years | | | | |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage | 0.25% | | | | |
Debt Instrument, Covenant, Fixed Charge Coverage Ratio | 1 | | | | |
Minimum Excess Availability Percentage of Maximum Revolver Amount | 10.00% | | | | |
Line of Credit Facility, Remaining Borrowing Capacity | | | | $ 43,200,000 | |
Debt, Weighted Average Interest Rate | | | | 2.84% | |
Letters of Credit Outstanding, Amount | | | | $ 4,700,000 | |
Long-term Line of Credit | | | | 80,175,000 | $ 96,600,000 |
Revolving Credit Facility [Member] | Overnight Borrowings [Member] | | | | | |
Long-term Line of Credit | | | | $ 0 | |
Revolving Credit Facility [Member] | Eligible Investment Grade Accounts Receivable [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 85.00% | | | | |
Revolving Credit Facility [Member] | Eligible Investment Grade Accounts Receivable [Member] | Minimum [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 85.00% | | | | |
Revolving Credit Facility [Member] | Eligible Investment Grade Accounts Receivable [Member] | Maximum [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 90.00% | | | | |
Revolving Credit Facility [Member] | Eligible Unbilled Accounts Receivable [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 85.00% | | | | |
Revolving Credit Facility [Member] | Eligible Revenue Equipment [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 85.00% | | | | |
Borrowing Base Before Additions | $ 10,000,000 | | | | |
Revolving Credit Facility [Member] | Newly Acquired Revenue Equipment [Member] | | | | | |
Borrowing Based Treshhold, Percentage | 85.00% | | | | |
Revolving Credit Facility [Member] | Scenario, Forecast [Member] | | | | | |
Minimum Excess Availability Percentage of Maximum Revolver Amount | | 10.00% | | | |
Line of Credit Facility, Remaining Borrowing Capacity | | $ 17,000,000 | $ 34,000,000 | | |
Availability Percentage of Maximum Revolver Amount | | | 20.00% | | |
Revolving Credit Facility [Member] | Base Rate [Member] | Through May 31, 2016 [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 0.50% | | | | |
Revolving Credit Facility [Member] | Base Rate [Member] | Through May 31, 2016 [Member] | Minimum [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 0.25% | | | | |
Revolving Credit Facility [Member] | Base Rate [Member] | Through May 31, 2016 [Member] | Maximum [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 1.00% | | | | |
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Through May 31, 2016 [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 1.50% | | | | |
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | After May 31, 2016 [Member] | Minimum [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 1.25% | | | | |
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | After May 31, 2016 [Member] | Maximum [Member] | | | | | |
Debt Instrument, Basis Spread on Variable Rate | 2.00% | | | | |
Letter of Credit Sub Facility [Member] | | | | | |
Line of Credit Facility, Maximum Borrowing Capacity | $ 15,000,000 | | | | |
Swing Line Sub Facility [Member] | | | | | |
Line of Credit Facility, Maximum Borrowing Capacity | $ 20,000,000 | | | | |