Note 8 - Derivative Instruments (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

Schedule of Foreign Exchange Contracts, Statement of Financial Position [Table Text Block]

	June 30,		December 31,
Balance sheet line item:	2021		2020
Current derivatives assets	$	5.5	$	3.5
Non-current derivatives assets		4.9		4.2

Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block]

June 30, 2021	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver		Gold		Zinc		Lead		Silver		Gold		Zinc		Lead
	(ounces)		(ounces)		(pounds)		(pounds)		(ounces)		(ounces)		(pounds)		(pounds)
Contracts on provisional sales
2021 settlements		2,344		7		17,857		11,762	$	26.76	$	1,810	$	1.32	$	1.00
Contracts on forecasted sales
2021 settlements		—		—		15,708		14,991		N/A		N/A	$	1.24	$	0.94
2022 settlements		—		—		66,855		50,982		N/A		N/A	$	1.28	$	0.96
2023 settlements		—		—		76,280		52,249		N/A		N/A	$	1.29	$	1.00
2024 settlements		—		—		15,047		—		N/A		N/A	$	1.33		N/A

December 31, 2020	Ounces/pounds under contract (in 000's)								Average price per ounce/pound
	Silver		Gold		Zinc		Lead		Silver		Gold		Zinc		Lead
	(ounces)		(ounces)		(pounds)		(pounds)		(ounces)		(ounces)		(pounds)		(pounds)
Contracts on provisional sales
2021 settlements		1,282		4		23,314		4,905	$	25.00	$	1,858	$	1.19	$	0.90
Contracts on forecasted sales
2021 settlements		—		—		41,577		30,876		N/A		N/A	$	1.17	$	0.88
2022 settlements		—		—		18,519		—		N/A		N/A	$	1.28		N/A

Schedule of Derivatives Instruments Statements of Financial Performance and Financial Position, Location [Table Text Block]

	June 30, 2021								December 31, 2020
Balance sheet line item:	Contracts in an asset position		Contracts in a liability position			Net asset (liability)			Contracts in an asset position		Contracts in a liability position			Net asset (liability)
Current derivatives assets	$	0.7	$	(0.3	)	$	0.4		$	0.2	$	(0.2	)	$	—
Non-current derivatives assets		—		—			—			0.5		(0.1	)		0.4
Current derivatives liabilities		2.1		(8.9	)		(6.8	)		0.1		(11.8	)		(11.7	)
Non-current derivatives liabilities		0.9		(8.0	)		(7.1	)		—		—			—