Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy	12 Months Ended
	Dec. 31, 2015 $ / shares $ / oz
$30 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	30
Quarterly dividend per share	$ 0.01
Annual dividend per share	$ 0.04
$35 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	35
Quarterly dividend per share	$ 0.02
Annual dividend per share	$ 0.08
$40 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	40
Quarterly dividend per share	$ 0.03
Annual dividend per share	$ 0.12
$45 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	45
Quarterly dividend per share	$ 0.04
Annual dividend per share	$ 0.16
$50 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	50
Quarterly dividend per share	$ 0.05
Annual dividend per share	$ 0.20
$55 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	55
Quarterly dividend per share	$ 0.06
Annual dividend per share	$ 0.24
$60 [Member]
Note 9 - Stockholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce) | $ / oz	60
Quarterly dividend per share	$ 0.07
Annual dividend per share	$ 0.28