Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue
Revenue	$ 227,574	$ 61,036	$ 5,216
Cost and expenses
Other operating costs and expenses		258	416
Asset retirement obligation accretion	494	405	229
Depreciation and amortization	12,423	3,154	252
Selling, general and administrative	14,006	12,591	7,452
Total cost and expenses	203,478	76,929	12,746
Operating income (loss)	24,096	(15,893)	(7,530)
Interest and dividend income	36	295	139
Other income	2,518	204
Interest expense	(1,463)	(23)	(124)
Income (loss) before tax	25,187	(15,417)	(7,515)
Income tax expense	113
Net income (loss)	$ 25,074	$ (15,417)	$ (7,515)
Earnings (loss) per common share
Basic earnings (loss) per share (in dollars per share)	$ 0.63	$ (0.41)
Diluted earnings (loss) per share (in dollars per share)	$ 0.62	$ (0.41)
Basic weighted average shares outstanding (in shares)	40,039	37,578
Diluted weighted average shares outstanding (in shares)	40,263	37,578
Coal Sales [Member]
Revenue
Revenue	$ 227,574	$ 58,798	$ 2,167
Cost and expenses
Cost of coal sales (exclusive of items shown separately below)	176,555	58,308	1,796
Coal Processing [Member]
Revenue
Revenue		2,238	3,049
Cost and expenses
Cost of coal sales (exclusive of items shown separately below)		$ 2,213	$ 2,601