Note 9 - Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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
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
May 6, 2015	$	—	$	0.0025	$	—	$	0.0025	$	0.9	June 2015
August 6, 2015	$	—	$	0.0025	$	—	$	0.0025	$	0.9	September 2015
November 3, 2015	$	—	$	0.0025	$	—	$	0.0025	$	0.9	December 2015
February 20, 2016	$	—	$	0.0025	$	—	$	0.0025	$	0.9	March 2016
May 4, 2016	$	—	$	0.0025	$	—	$	0.0025	$	1.0	June 2016
August 3, 2016	$	—	$	0.0025	$	—	$	0.0025	$	1.0	September 2016
November 4, 2016	$	—	$	0.0025	$	—	$	0.0025	$	1.0	December 2016
February 21, 2017	$	—	$	0.0025	$	—	$	0.0025	$	1.0	March 2017

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, 2016		3,375,798		$	2.73
Granted (unvested)		1,138,669		$	4.40
Canceled		(205,032	)	$	2.70
Distributed (vested)		(1,573,871	)	$	2.82
Unvested, December 31, 2016		2,735,564		$	3.41

Schedule of Share-based Compensation, Unvested Shares Expected to Vest [Table Text Block]

790,253	in June 2017
650,137	in July 2017
379,743	in June 2018
579,437	in July 2018
335,994	in June 2019