Note 8 - Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2021

Notes Tables

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

	March 31,		December 31,
Balance sheet line item:	2021		2020
Current derivatives assets	$	5.0	$	3.5
Non-current derivatives assets		4.2		4.2

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

March 31, 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		1,492		5		12,070		1,587	$	25.48	$	1,736	$	1.26	$	0.89
Contracts on forecasted sales
2021 settlements		—		—		33,841		30,479		N/A		N/A	$	1.20	$	0.89
2022 settlements		—		—		53,407		42,715		N/A		N/A	$	1.26	$	0.96
2023 settlements		—		—		41,171		—		N/A		N/A	$	1.27		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]

	March 31, 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	$	3.3	$	(1.1	)	$	2.2		$	0.2	$	(0.2	)	$	—
Non-current derivatives assets		2.3		(0.2	)		2.1			0.5		(0.1	)		0.4
Current derivatives liability		—		(3.9	)		(3.9	)		0.1		(11.8	)		(11.7	)
Other non-current liabilities		0.4		(1.2	)		(0.8	)		—		—			—