Provision for Site Reclamation and Closure (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Provision For Site Reclamation And Closure [Abstract]

Summary of Detailed Information about Provision for Site Reclamation and Closure

Balance at December 31, 2016	$	3,148
Accretion of discounted cash flows		230
Change in estimated cash flows and assumptions		723
Balance at December 31, 2017	$	4,101
Addition of Florida Canyon Mine at the Closing Date		30,227
Accretion of discounted cash flows		876
Change in estimated cash flows and assumptions		2,426
Balance at December 31, 2018	$	37,630