Note 9 - Shareholders' Equity (Details) - Common Stock Dividends Declared by our Board of Directors (USD $) In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013
November 8, 2011 [Member]
Dividends Payable [Line Items]
(A) Silver-price-linked component per share	$ 0.02
(A+B+C) Total dividend per share	$ 0.02
Total dividend (in Dollars)	$ 5.6
February 17, 2012 [Member]
Dividends Payable [Line Items]
(A) Silver-price-linked component per share	$ 0.01
(A+B+C) Total dividend per share	$ 0.0125
Total dividend (in Dollars)	3.6
(B) Minimum annual component per share	$ 0.0025
May 8, 2012 [Member]
Dividends Payable [Line Items]
(A) Silver-price-linked component per share	$ 0.02
(A+B+C) Total dividend per share	$ 0.0225
Total dividend (in Dollars)	6.4
(B) Minimum annual component per share	$ 0.0025
August 7, 2012 [Member]
Dividends Payable [Line Items]
(A+B+C) Total dividend per share	$ 0.0025
Total dividend (in Dollars)	0.7
(B) Minimum annual component per share	$ 0.0025
November 2, 2012 [Member]
Dividends Payable [Line Items]
(A) Silver-price-linked component per share	$ 0.02
(A+B+C) Total dividend per share	$ 0.0225
Total dividend (in Dollars)	6.4
(B) Minimum annual component per share	$ 0.0025
February 25, 2013 [Member]
Dividends Payable [Line Items]
(C) Special dividend per share	$ 0.01
(A+B+C) Total dividend per share	$ 0.0125
Total dividend (in Dollars)	3.6
(B) Minimum annual component per share	$ 0.0025
May 10, 2013 [Member]
Dividends Payable [Line Items]
(A+B+C) Total dividend per share	$ 0.0025
Total dividend (in Dollars)	0.7
(B) Minimum annual component per share	$ 0.0025
August 8, 2013 [Member]
Dividends Payable [Line Items]
(A+B+C) Total dividend per share	$ 0.0025
Total dividend (in Dollars)	0.9
(B) Minimum annual component per share	$ 0.0025
November 5, 2013 [Member]
Dividends Payable [Line Items]
(A+B+C) Total dividend per share	$ 0.0025
Total dividend (in Dollars)	$ 0.9
(B) Minimum annual component per share	$ 0.0025