Conveyance of Future Hard Minerals Royalty Revenues (Tables)

12 Months Ended

Dec. 31, 2017

Deferred Revenue Disclosure [Abstract]

Schedule of Future Royalty Payments

The following summarizes the remaining amounts that the Company expects to pay, prior to the potential 3% to 4% of any excess described above:

millions
2018	$	50
2019	52
2020	56
2021	57
2022	58
Later years	204
Total	$	477