Note 11 - Derivative Instruments (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

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

	December 31,
Balance sheet line item:	2020		2019
Other current assets	$	3.5	$	0.6
Other non-current assets		4.2		0.6
Current derivatives liability		—		0.4
Other non-current assets		—		1.0

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

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		—		—		41,557		30,876		N/A		N/A	$	1.17	$	0.88
2022 settlements		—		—		18,519		—		N/A		N/A	$	1.28		N/A

December 31, 2019	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
2020 settlements		2,556		10		21,550		5,159	$	17.20	$	1,481	$	1.04	$	0.88
Contracts on forecasted sales
2020 settlements		—		—		441		11,740		N/A		N/A	$	1.13	$	0.98

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

	December 31, 2020								December 31, 2019
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)
Other current assets	$	0.2	$	(0.2	)	$	—		$	—	$	—		$	—
Other non-current assets		0.5		(0.1	)		0.4			—		—			—
Current derivatives liability		0.1		(11.8	)		(11.7	)		2.1		(7.9	)		(5.8	)