Investments (Tables)

12 Months Ended

Dec. 31, 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 December 31, 2017
In thousands	Cost		Gross Unrealized Losses			Gross Unrealized Gains		Estimated Fair Value
Equity Securities
Metalla Royalty & Streaming Ltd.	$	6,294	$	—		$	1,354	$	7,648
Corvus Gold Inc.	3,582		—			4,518		8,100
Almaden Minerals, Ltd.	3,125		(235		)	—		2,890
Northern Empire Resources Corp.	4,489		—			1,077		5,566
Rockhaven Resources, Ltd.	2,064		(193		)	—		1,871
Kootenay Silver, Inc.	738		—			1		739
Other	1,479		(453		)	405		1,431
Equity securities	$	21,771	$	(881	)	$	7,355	$	28,245
Debt Securities
Metalla Royalty & Streaming Ltd.	$	6,677	$	(85	)	$	—	$	6,592
Equity and debt securities	$	28,448	$	(966	)	$	7,355	$	34,837

	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 and debt 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 December 31, 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	$	881	$	5,662	$	—	$	—	$	881	$	5,662
Debt securities	85		6,592		—		—		85		6,592