Note 9 - Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2014

Stockholders' Equity Note [Abstract]

Schedule of Potential Per Share Dividend Amounts Quarterly Price Levels [Table Text Block]

Quarterly average realized silver price per ounce		Quarterly dividend per share		Annual dividend per share
$	30	$	0.01	$	0.04
$	35	$	0.02	$	0.08
$	40	$	0.03	$	0.12
$	45	$	0.04	$	0.16
$	50	$	0.05	$	0.20
$	55	$	0.06	$	0.24
$	60	$	0.07	$	0.28

Schedule of Dividends Payable [Table Text Block]

	(A)		(B)		(C)		(A+B+C)
Declaration date	Silver-price- linked component per share		Minimum annual component per share		Special dividend per share		Total dividend per share		Total dividend amount (in millions)		Month of payment
November 8, 2011	$	0.02	$	—	$	—	$	0.02	$	5.6	December 2011
February 17, 2012	$	0.01	$	0.0025	$	—	$	0.0125	$	3.6	March 2012
May 8, 2012	$	0.02	$	0.0025	$	—	$	0.0225	$	6.4	June 2012
August 7, 2012	$	—	$	0.0025	$	—	$	0.0025	$	0.7	September 2012
November 2, 2012	$	0.02	$	0.0025	$	—	$	0.0225	$	6.4	December 2012
February 25, 2013	$	—	$	0.0025	$	0.01	$	0.0125	$	3.6	March 2013
May 10, 2013	$	—	$	0.0025	$	—	$	0.0025	$	0.7	June 2013
August 8, 2013	$	—	$	0.0025	$	—	$	0.0025	$	0.9	August 2013
November 5, 2013	$	—	$	0.0025	$	—	$	0.0025	$	0.9	December 2013
February 21, 2014	$	—	$	0.0025	$	—	$	0.0025	$	0.9	March 2014
May 5, 2014	$	—	$	0.0025	$	—	$	0.0025	$	0.9	June 2014
July 31, 2014	$	—	$	0.0025	$	—	$	0.0025	$	0.9	September 2014
November 5, 2014	$	—	$	0.0025	$	—	$	0.0025	$	0.9	December 2014
February 17, 2015	$	—	$	0.0025	$	—	$	0.0025	$	0.9	March 2015

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Shares Subject to Options			Weighted Average Exercise Price
Outstanding, December 31, 2013		612,745		$	4.29
Expired		(353,403	)	$	3.42
Outstanding, December 31, 2014		259,342		$	5.47

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Shares			Weighted Average Grant Date Fair Value per Share
Unvested, January 1, 2014		2,085,301		$	3.56
Granted		1,457,267		$	3.30
Canceled		(72,031	)	$	3.10
Distributed		(1,234,962	)	$	3.74
Unvested, December 31, 2014		2,235,575		$	3.31