Subsequent Event (Details)				3 Months Ended		6 Months Ended
	Aug. 05, 2016 USD ($) item	Aug. 02, 2016 USD ($) shares	Mar. 24, 2015 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2015 shares	Jun. 30, 2016 USD ($) shares	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Subsequent Events
Proceeds from sale of assets						$ 50,000	$ 301,000
Property value						9,842,000		$ 11,125,000
Gain on sale of assets						$ 45,000	$ 256,000
Junior Mining Company
Subsequent Events
Shares received | shares					5,000,000
Investment shares held (in shares) | shares						5,000,000
Ownership interest in outstanding common stock (as a percent)						9.00%
Junior Mining Company | Subsequent Event
Subsequent Events
Shares received | shares		2,500,000
Investment shares held (in shares) | shares		7,500,000
Ownership interest in outstanding common stock (as a percent)		10.00%
San Diego
Subsequent Events
Property value						$ 0
Additional payments in joint venture			$ 800,000
Additional interest in joint venture			10.00%
San Diego | Subsequent Event
Subsequent Events
Ownership in property (as a percent)		50
Gain on sale of assets				$ 500,000
San Diego | Junior Mining Company
Subsequent Events
Ownership in property (as a percent)					50
San Diego | Junior Mining Company | Subsequent Event
Subsequent Events
Ownership in property (as a percent)		50
Proceeds from sale of assets		$ 379,000
Net smelter return royalty (as a percent)		2.0
Celaya | Subsequent Event
Subsequent Events
Ownership in property (as a percent)	20
Gain on sale of assets				$ 200,000
Celaya | Subsequent Event | Second earn-in period
Subsequent Events
Ownership in property (as a percent)	40
Number of representatives | item	1
Electrum | Celaya | Subsequent Event
Subsequent Events
Proceeds from sale of assets	$ 200,000
Electrum | Celaya | Subsequent Event | Year one
Subsequent Events
Additional payments in joint venture	$ 500,000
Electrum | Celaya | Subsequent Event | Initial earn-in period
Subsequent Events
Ownership in property (as a percent)	60
Additional payments in joint venture	$ 2,500,000
Agreement period	3 years
Electrum | Celaya | Subsequent Event | Second earn-in period
Subsequent Events
Ownership in property (as a percent)	80
Additional payments in joint venture	$ 2,500,000
Agreement period	3 years
Number of representatives | item	2
Additional interest in joint venture	20.00%
Minimum | Celaya | Subsequent Event
Subsequent Events
Ownership in property (as a percent)	10