Acquisitions Paramount (Details) - Paramount Gold and Silver Corp. [Member] $ in Thousands	Apr. 17, 2015 USD ($)
Business Acquisition [Line Items]
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 188,817
Business Combination, Consideration Transferred, Purchase Price	201,367
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets	$ 307,193
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable, Conversion Ratio	0.2016
Payments to Acquire Businesses, Gross	$ 8,530
Business Acquisition, Transaction Costs	4,020
Business Combination, Separately Recognized Transactions, Payments to Acquire Additional Interests	$ 1,500
Noncontrolling Interest, Ownership Percentage by Parent	4.90%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities	$ 105,826
Business Combination, Consideration Transferred	$ 201,367