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Note 9 - Debt, Credit Facilities and Leases (Details Textual) $ in Millions |  |  | 3 Months Ended | 12 Months Ended |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 01, 2019 | Apr. 12, 2013 USD ($) | Mar. 31, 2019 USD ($) | Mar. 31, 2018 USD ($) | Dec. 31, 2014 USD ($) | Jan. 01, 2020 | Oct. 01, 2019 | Apr. 01, 2019 | 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 |  |  |  | $ 3,000,000 |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Total |  |  |  | 15,160,000 |  |  |  |  |  |  | $ 13,100,000 |  |  |  |
Finance Lease, Liability, Current |  |  |  | 5,858,000 |  |  |  |  |  |  | 5,264,000 |  |  |  |
Finance Lease, Liability, Noncurrent |  |  |  | 9,302,000 |  |  |  |  |  |  | 7,871,000 |  |  |  |
Finance Lease, Right-of-Use Asset |  |  |  | 21,900,000 |  |  |  |  |  |  | 20,000,000 |  |  |  |
Finance Lease, Right-of-Use Asset, Amortization |  |  |  | 1,600,000 |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Interest Expense |  |  |  | 200,000 |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Payment, Due, Total |  |  |  | 16,185,000 |  |  |  |  |  |  |  |  |  |  |
Finance Lease, Liability, Undiscounted Excess Amount |  |  |  | 1,025,000 |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Liability, Total |  |  |  | 20,665,000 |  |  |  |  |  | $ 22,400,000 |  |  |  |  |
Operating Lease, Liability, Current |  |  |  | 6,701,000 |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Liability, Noncurrent |  |  |  | 13,964,000 |  |  |  |  |  |  |  |  |  |  |
Operating Lease, Right-of-Use Asset |  |  |  | 20,647,000 |  |  |  |  |  | $ 22,400,000 |  |  |  |  |
Operating Lease, Expense |  |  |  | 2,100,000 |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Liability, Payments, Due, Total |  |  |  | $ 22,899,000 |  |  |  |  |  |  |  |  |  |  |
Minimum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Discount Rate |  |  |  | 5.00% |  |  |  |  |  |  |  |  |  |  |
Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Ratio | [1] |  |  | 4.5 |  |  |  |  |  |  |  |  |  |  |
Lessee, Operating Lease, Discount Rate |  |  |  | 6.50% |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of Credit Facility, Maximum Borrowing Capacity |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000 |  |  | $ 100,000,000
Long-term Line of Credit, Total |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |
Repayments of Lines of Credit |  |  |  | 58,000,000 |  |  |  |  |  |  |  |  |  |  |
Proceeds from Lines of Credit, Total |  |  |  | 85,000,000 |  |  |  |  |  |  |  |  |  |  |
Revolving Credit Facility [Member] | Forecast [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Ratio |  |  |  |  |  |  | 4 | 4.5 |  |  |  |  |  |  |
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% |  |  |
Subsequent Event [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Leverage Ratio |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  | $ 500,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Payment for Pension Benefits |  |  |  |  |  | $ 6,500,000 |  |  |  |  |  |  |  |  |
Proceeds from Issuance of Senior Long-term Debt |  |  | $ 490,000,000 |  |  |  |  |  |  |  |  |  |  |  |
Underwriting Discount on Senior Notes |  |  | 2.00% |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unamortized Discount, Total |  |  | $ 10,000,000 | 2,700,000 |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Interest Rate, Stated Percentage |  |  | 6.875% |  |  |  |  |  |  |  |  |  |  |  |
Interest Expense, Debt, Total |  |  |  | 9,100,000 | $ 9,100,000 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Redemption Price, Percentage |  |  | 101.00% |  |  |  |  |  |  |  |  |  |  |  |
Senior Notes [Member] | Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Redemption Price, Percentage |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Series 2018-A Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Face Amount |  |  |  |  |  |  |  |  |  |  |  |  | $ 30,800,000 | $ 40.0 |
Debt Instrument, Unamortized Discount, Total |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.2 |
Debt Instrument, Interest Rate, Stated Percentage |  |  |  |  |  |  |  |  |  |  |  |  | 4.68% | 4.68% |
Interest Expense, Debt, Total |  |  |  | $ 400,000 | $ 400,000 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Issuance, Discount Rate |  |  |  |  |  |  |  |  |  |  |  |  | 0.58% | 0.58% |
[1] | The leverage ratio changed to 5.00:1 effective April 1, 2019, will return to 4.50:1 effective October 1, 2019, and then change to 4.00:1 effective January 1, 2020.

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- Definition Percentage of fronting fee to each issuing bank annually on the average dollar amount of any outstanding letters of credit. + References No definition available. + Details
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- Definition Amount of lessee's right to use underlying asset under finance lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918627-209977 + Details
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