Note 8 - Shareholders' Equity (Details) - Common Stock Dividend Policy - 3 months ended Jun. 30, 2015	$ / shares $ / oz
$30 [Member]
Note 8 - Shareholders' 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 8 - Shareholders' 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 8 - Shareholders' 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 8 - Shareholders' 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 8 - Shareholders' 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