Note 8 - Shareholders' Equity (Details) - Common Stock Dividend Policy (USD $)	3 Months Ended
	Mar. 31, 2015
$30 [Member]
Note 8 - Shareholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce)	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)	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)	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)	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)	50
Quarterly dividend per share	$ 0.05
Annual dividend per share	$ 0.20
$55 [Member]
Note 8 - Shareholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce)	55
Quarterly dividend per share	$ 0.06
Annual dividend per share	$ 0.24
$60 [Member]
Note 8 - Shareholders' Equity (Details) - Common Stock Dividend Policy [Line Items]
Quarterly average realized silver price per ounce (in Dollars per Ounce)	60
Quarterly dividend per share	$ 0.07
Annual dividend per share	$ 0.28