CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Common Stock Registered direct purchase agreement	Common Stock	Additional Paid-in Capital Registered direct purchase agreement	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive income (loss)	Registered direct purchase agreement	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		$ 4		133				137
Stock compensation accrued and shares issued for vested stock awards (in shares)		437,279
Registered direct purchase agreement, net	$ 32		$ 1,210				$ 1,242
Registered direct purchase agreement, net (in shares)	3,153,808
Deemed dividend on warrants				8	(8)
Net loss					(2,424)			(2,424)
Balance at Jun. 30, 2018		$ 955		$ 517,635	$ (511,604)			$ 6,986
Balance (in shares) at Jun. 30, 2018		95,520,796