Investments (Tables)

6 Months Ended

Jun. 30, 2017

Investment in Marketable Securities [Abstract]

Investments

These investments are classified as available-for-sale and are measured at fair value in the financial statements with unrealized gains and losses recorded in Other comprehensive income (loss).

	At June 30, 2017
In thousands	Cost		Gross Unrealized Losses			Gross Unrealized Gains		Estimated Fair Value
Almaden Minerals, Ltd.	$	3,125	$	—		$	461	$	3,586
Northern Empire Resources Corp.	2,999		—			41		3,040
Rockhaven Resources, Ltd.	2,064		(197		)	—		1,867
Kootenay Silver, Inc.	1,291		—			—		1,291
Other	1,518		(45		)	615		2,088
Equity securities	$	10,997	$	(242	)	$	1,117	$	11,872

	At December 31, 2016
In thousands	Cost		Gross Unrealized Losses		Gross Unrealized Gains		Estimated Fair Value
Kootenay Silver, Inc.	$	2,645	$	—	$	—	$	2,645
Silver Bull Resources, Inc.	233		—		783		1,016
Other	229		—		598		827
Equity securities	$	3,107	$	—	$	1,381	$	4,488

Schedule of Unrealized Loss on Investments [Table Text Block]

The following table summarizes unrealized losses on equity securities for which other-than-temporary impairments have not been recognized and the fair values of those securities, aggregated by the length of time the individual securities have been in a continuous unrealized loss position, at June 30, 2017:

	Less than twelve months					Twelve months or more				Total
In thousands	Unrealized Losses			Fair Value		Unrealized Losses		Fair Value		Unrealized Losses			Fair Value
Equity securities	$	(242	)	$	2,083	$	—	$	—	$	(242	)	$	2,083