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Note 9 - Debt, Credit Facility and Leases (Details Textual) $ in Thousands, $ in Millions |  |  | 9 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 01, 2019 | Apr. 12, 2013 USD ($) | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($) | Dec. 31, 2014 USD ($) | Jul. 01, 2020 | Apr. 01, 2020 | Jan. 01, 2020 | Dec. 31, 2019 | Oct. 01, 2019 | Jul. 31, 2019 USD ($) | Jan. 01, 2019 USD ($) | Dec. 31, 2018 USD ($) | Jul. 31, 2018 USD ($) | Mar. 05, 2018 USD ($) | Mar. 05, 2018 CAD ($) | May 31, 2016 USD ($)
Letters of Credit Outstanding, Amount |  |  | $ 38,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Total |  |  | 14,275 |  |  |  |  |  |  |  |  |  | $ 13,100 |  |  |  |
Finance Lease, Liability, Current |  |  | 5,704 |  |  |  |  |  |  |  |  |  | 5,264 |  |  |  |
Finance Lease, Liability, Noncurrent |  |  | 8,569 |  |  |  |  |  |  |  |  |  | 7,871 |  |  |  |
Finance Lease, Right-of-Use Asset |  |  | 21,400 |  |  |  |  |  |  |  |  |  | 20,000 |  |  |  |
Finance Lease, Right-of-Use Asset, Amortization |  |  | 5,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Interest Expense |  |  | 600 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Payment, Due, Total |  |  | 15,243 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Undiscounted Excess Amount |  |  | $ 968 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Weighted Average Remaining Lease Term |  |  | 1 year 10 months 24 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Liability, Total |  |  | $ 17,330 |  |  |  |  |  |  |  |  | $ 22,400 |  |  |  |  |
Operating Lease, Liability, Current |  |  | 5,864 |  |  |  |  |  |  |  |  |  | 0 |  |  |  |
Operating Lease, Liability, Noncurrent |  |  | 11,466 |  |  |  |  |  |  |  |  |  | 0 |  |  |  |
Operating Lease, Right-of-Use Asset |  |  | 17,313 |  |  |  |  |  |  |  |  | $ 22,400 | $ 0 |  |  |  |
Operating Lease, Expense |  |  | 5,700 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Liability, Payments, Due, Total |  |  | $ 17,393 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Weighted Average Remaining Lease Term |  |  | 4 years 8 months 12 days |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Discount Rate |  |  | 5.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Discount Rate |  |  | 6.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  |  |  |  |  |  |  | $ 150,000 |  |  | $ 250,000 |  |  | $ 100,000
Leverage Ratio |  |  | 6.50 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Lines of Credit, Total |  |  | $ 50,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Ratio |  |  |  |  |  |  |  |  |  | 6.00 |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Ratio |  |  |  |  |  | 4.00 | 5.00 | 5.50 | 6.00 |  |  |  |  |  |  |  |
Letter of Credit [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letter of Credit Outstanding, Fronting Fee |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.20% |  |  |
Letter of Credit [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letter of Credit, Participation Fee, Percent |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.25% |  |  |
Letter of Credit [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Letter of Credit, Participation Fee, Percent |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.25% |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  | $ 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payment for Pension Benefits |  |  |  |  | $ 6,500 |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Senior Long-term Debt |  | $ 490,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Underwriting Discount on Senior Notes |  | 2.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount, Total |  | $ 10,000 | 2,100 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  | 6.875% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest Expense, Debt, Total |  |  | 27,200 | $ 27,200 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Redemption Price, Percentage | 100.00% | 101.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Series 2018-A Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,800 | $ 40.0 |
Debt Instrument, Unamortized Discount, Total |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.2 |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.68% | 4.68% |
Interest Expense, Debt, Total |  |  | $ 1,100 | $ 1,100 |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Issuance, Discount Rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0.58% | 0.58% |

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