Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2015

Asset Retirement Obligation Disclosure [Abstract]

Schedule of changes in carrying amount of asset retirement obligations

		2015		2014
Balance as of January 1		$	217,312	$	247,329
Reduction in asset retirement obligation attributable to sale of Decker
	Mine interest (see Note 4)		—		(72,175)
Accretion expense			12,555		15,136
Revisions to estimated future reclamation cash flows			(75,779)		28,243
Payments			(933)		(1,221)
Balance as of December 31			153,155		217,312
Less: current portion			(1,400)		(1,071)
	Asset retirement obligation, net of current portion	$	151,755	$	216,241