Note 7 - Debt, Credit Facility and Leases (Details Textual) $ in Thousands, shares in Millions, $ in Millions							1 Months Ended		12 Months Ended
	Feb. 16, 2026	Oct. 09, 2020 CAD ($)	Sep. 09, 2020 CAD ($)	Aug. 09, 2020 CAD ($)	Jul. 09, 2020 CAD ($)	Mar. 19, 2020 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2019 CAD ($) shares	Feb. 15, 2026	Feb. 15, 2025	Feb. 15, 2024	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jul. 09, 2020 USD ($)	Jul. 09, 2020 CAD ($)	Feb. 19, 2020 USD ($)	Jul. 31, 2018 USD ($)	Mar. 05, 2018 USD ($)	Mar. 05, 2018 CAD ($)	May 31, 2016 USD ($)
Proceeds from Issuance of Long-term Debt, Total												$ 716,327	$ 279,500	$ 102,024
Payments of Debt Issuance Costs												1,356	976	2,638
Paid-in-Kind Prepayment of Debt Fee												0	2,855	0
Finance Lease, Liability, Total							$ 12,600					15,765	12,600
Finance Lease, Liability, Current							5,429					6,491	5,429
Finance Lease, Liability, Noncurrent							7,214					9,274	7,214
Finance Lease, Right-of-Use Asset, after Accumulated Amortization, Total							20,600					22,300	20,600
Finance Lease, Right-of-Use Asset, Amortization												7,400	5,900	5,300
Finance Lease, Interest Expense												600	700	700
Finance Lease, Liability, Payment, Due, Total												16,819
Finance Lease, Liability, Undiscounted Excess Amount												$ 1,054
Finance Lease, Weighted Average Remaining Lease Term (Year)												2 years
Finance Lease, Weighted Average Discount Rate, Percent												6.70%
Operating Lease, Liability, Total												$ 10,642
Operating Lease, Liability, Current							5,580					3,008	5,580
Operating Lease, Liability, Noncurrent							10,818					7,634	10,818
Operating Lease, Right-of-Use Asset							$ 16,381					10,628	16,381
Operating Lease, Expense												7,200	7,500
Lessee, Operating Lease, Liability, to be Paid, Total												$ 12,622
Operating Lease, Weighted Average Remaining Lease Term (Year)												5 years 4 months 24 days
Maximum [Member]
Lessee, Operating Lease, Discount Rate												6.50%
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity																		$ 250,000			$ 100,000
Letters of Credit Outstanding, Amount												$ 20,300
Proceeds from Lines of Credit, Total												210,000
Repayments of Lines of Credit												210,000
Long-term Line of Credit, Total												0
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																		4.00%
Conversion of Series 2018A Senior Notes Into Common Stock [Member]
Debt Conversion, Converted Instrument, Shares Issued (in shares) | shares							10.7	10.7
Debt Conversion, Converted Instrument, Amount							$ 33,500	$ 43.8
Senior Notes [Member]
Long-term Debt, Gross												512,886
Interest Expense, Debt, Total												40,200	$ 36,300	36,300
Long-term Debt, Total												$ 507,242
Senior Notes [Member] | The 2028 Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage												7.25%					7.25%
Long-term Debt, Gross												$ 475,000
Debt Instrument, Face Amount																	$ 475,000
Proceeds from Issuance of Long-term Debt, Total						$ 469,500
Underwriting Discount on Senior Notes																	1.16%
Debt Instrument, Unamortized Discount, Total																	$ 5,500
Debt Instrument, Redemption Price, Percentage												100.00%
Debt Instrument, Redemption Price, Percentage, Net of Cash Proceeds of Equity Offerings												35.00%
Debt Instrument, Redemption Price, Percentage, Including Accrued and Unpaid Interest												101.00%
Long-term Debt, Total												$ 468,538
Senior Notes [Member] | The 2028 Senior Notes [Member] | Forecast [Member]
Debt Instrument, Redemption Price, Percentage	100.00%								101.813%	103.625%	105.438%
Senior Notes [Member] | The 2021 Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage							6.875%						6.875%
Long-term Debt, Gross							$ 506,500						$ 506,500
Debt Instrument, Unamortized Discount (Premium), Net, Total												1,700
Long-term Debt, Total							$ 504,729						504,729
Senior Notes [Member] | IQ Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage															6.515%	6.515%
Long-term Debt, Gross												37,886
Debt Instrument, Face Amount															$ 36,800	$ 50.0
Interest Expense, Debt, Total												900
Debt Instrument, Unamortized Premium, Percentage of Principal															103.65%	103.65%
Debt Instrument, Unamortized Premium, Total																$ 1.8
Debt Instrument, Effective Annual Yield															5.74%	5.74%
Long-term Debt, Total												$ 38,704				$ 48.2
Debt Instrument, Number of Issuance Installments															4	4
Proceeds from Issuance of Debt		$ 12.5	$ 12.5	$ 12.5	$ 12.5
Payments of Debt Issuance Costs					$ 0.6
Debt Instrument, Covenant, Investment Over Next Four Years																$ 100.0
Series 2018-A Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage																			4.68%	4.68%
Debt Instrument, Face Amount																			$ 30,800	$ 40.0
Interest Expense, Debt, Total													4,200	$ 1,100
Paid-in-Kind Prepayment of Debt Fee													$ 2,900