Acquisitions - Northern Empire (Details) - Northern Empire Resources Corp.	1 Months Ended
	Oct. 31, 2018 USD ($) shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Common shares issued (value)	$ 63,887,000
Fair value of existing investment in Northern Empire	7,257,000
Transaction advisory fees and other acquisition costs			$ 2,449,000
Purchase price	$ 73,593,000
Assets:
Total assets acquired		$ 111,527,000
Liabilities:
Total liabilities assumed		37,934,000
Total assets acquired		$ 73,593,000
Common Stock
Business Acquisition [Line Items]
Common stock conversion ratio	0.1850
Common shares issued (in shares) | shares	12,100,000
Price per common share issued (UDS per share)			$ 5,270