MISCELLANEOUS OTHER INCOME (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income and Expenses [Abstract]
Contract Buyout	$ 8,410	$ 0	$ 8,410	$ 6,288
Purchased Coal Sales	3,569	1,908	9,667	2,512
Royalty Income - Non-Operated Coal	3,520	1,969	15,713	6,402
Rental Income	1,589	8,666	12,722	26,289
Right of Way Issuance	1,402	123	2,396	5,704
Interest Income	448	214	1,495	637
Other	775	689	2,105	1,870
Miscellaneous Other Income	$ 19,713	$ 13,569	$ 52,508	$ 49,702