MISCELLANEOUS OTHER INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Income and Expenses [Abstract]
Royalty Income - Non-Operated Coal	$ 4,976	$ 5,160	$ 16,863	$ 19,108
Purchased Coal Sales	3,136	2,901	9,052	15,389
Contract Buyout	1,193	0	3,583	350
Interest Income	755	523	2,399	1,591
Rental Income	625	896	1,923	3,066
Property Easements and Option Income	100	1,069	1,529	5,479
Other	403	429	1,325	2,251
Miscellaneous Other Income	$ 11,188	$ 10,978	$ 36,674	$ 47,234