CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive income (loss)	Total
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment related to change in accounting principle | Cumulative Effect Adjustment | ASU 2017-11 Earnings Per Share		$ 19,046	$ (17,148)		$ 1,898
Adjusted balance at beginning of period	$ 889	514,501	(505,185)	$ 55	10,260
Balance (Previously Reported) at Dec. 31, 2016	$ 889	495,455	(488,037)	55	8,362
Balance (in shares) (Previously Reported) at Dec. 31, 2016	89,020,041
Balance (in shares) at Dec. 31, 2016	89,020,041
Increase (Decrease) in Stockholders' Equity
Stock compensation accrued and shares issued for vested stock awards	$ 1	196			197
Stock compensation accrued and shares issued for vested stock awards (in shares)	200,000
Shares issued under the at-the-market offering agreement, net	$ 10	671			681
Shares issued under the at-the-market offering agreement, net (in shares)	1,024,392
Consideration shares sold to Hecla, net	$ 18	912			930
Consideration shares sold to Hecla, net (in shares)	1,811,015
Cancellation of treasury shares	$ 1	(1)
Cancellation of treasury shares (in shares)	(125,739)
Deemed dividend on warrants		5	(5)
Unrealized loss on marketable equity securities, net of tax				(95)	(95)
Net loss			(3,892)		(3,892)
Balance (Previously Reported) at Dec. 31, 2017	$ 919	516,284	(509,082)	(40)	8,081
Balance at Dec. 31, 2017					8,081
Balance (in shares) (Previously Reported) at Dec. 31, 2017	91,929,709
Balance (in shares) at Dec. 31, 2017	91,929,709
Increase (Decrease) in Stockholders' Equity
Cumulative adjustment related to change in accounting principle | Cumulative Effect Adjustment | ASU 2014-09 Revenue from Contracts with Customers			(89)	$ 40	(49)
Adjusted balance at beginning of period	$ 919	516,284	(509,172)		8,031
Stock compensation accrued and shares issued for vested stock awards		45			45
Net loss			(735)		(735)
Balance at Mar. 31, 2018	$ 919	$ 516,329	$ (509,907)		$ 7,341
Balance (in shares) at Mar. 31, 2018	91,929,709