Preference Rights Lease Application (PRLA) Settlement Income	9 Months Ended
Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Preference Rights Lease Application (PRLA) Settlement Income	Preference Rights Lease Application Settlement Income The Company recorded a $39.0 million gain during the quarter related to a settlement with the United States Department of Interior over a long-standing dispute, dating back to the 1970’s, on the valuation and disposition of Preference Rights Lease Application that Arch controlled in northwestern New Mexico with a joint venture partner. As part of the settlement, Arch will receive $67.0 million in the form of royalty credits on its federal coal leases which will be used to settle 50% of the Company’s monthly royalty obligations. The Company expects to realize the royalty credits beginning in September 2019 through the next 18-24 months depending on market conditions. Additionally, as part of the settlement, Arch will make a one-time payment of $27.0 million during October 2019 to its’ partner in the venture for their ownership interest in the underlying mineral reserves, as well as pay $1.0 million in closing fees.

Preference Rights Lease Application (PRLA) Settlement Income

9 Months Ended

Sep. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Preference Rights Lease Application (PRLA) Settlement Income

Preference Rights Lease Application Settlement Income

The Company recorded a $39.0 million gain during the quarter related to a settlement with the United States Department of Interior over a long-standing dispute, dating back to the 1970’s, on the valuation and disposition of Preference Rights Lease Application that Arch controlled in northwestern New Mexico with a joint venture partner. As part of the settlement, Arch will receive $67.0 million in the form of royalty credits on its federal coal leases which will be used to settle 50% of the Company’s monthly royalty obligations. The Company expects to realize the royalty credits beginning in September 2019 through the next 18-24 months depending on market conditions. Additionally, as part of the settlement, Arch will make a one-time payment of $27.0 million during October 2019 to its’ partner in the venture for their ownership interest in the underlying mineral reserves, as well as pay $1.0 million in closing fees.