Summary of Significant Accounting Policies Summary of Unearned Income (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Oct. 02, 2014
Contract Liabilities
Deferred Revenue Recognized	$ 16,226,000	$ 16,702,000	$ 1,857,000
Palmarejo gold production royalty
Contract Liabilities
Aggregate deposit to be received				$ 22,000,000
Price per ounce under agreement				$ 800
Production to be sold, percent				50.00%
Franco-Nevada
Contract Liabilities
Opening Balance	9,376,000	11,061,000	12,918,000
Deferred Revenue Recognized	(1,226,000)	(1,685,000)	(1,857,000)
Closing Balance	8,150,000	9,376,000	11,061,000
Kensington
Contract Liabilities
Opening Balance	15,003,000	15,009,000	0
Deferred Revenue, Additions	30,013,000	30,177,000	40,009,000
Deferred Revenue Recognized	(30,000,000)	(30,183,000)	(25,000,000)
Closing Balance	15,016,000	15,003,000	$ 15,009,000
Kensington | December 2020 Prepayment [Member]
Contract Liabilities
Opening Balance	15,000,000
Deferred Revenue Recognized	$ 15,000,000
Closing Balance		$ 15,000,000