CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 161,434	$ 212,793
Trade accounts receivable, net of allowance for doubtful accounts of $432 and $0 as of September 30, 2020 and December 31, 2019	179,671	244,666
Inventories, net	124,245	162,659
Prepaid expenses and other current assets	120,939	91,361
Total current assets	586,289	711,479
Property, plant, and equipment, net of accumulated depreciation and amortization of $395,397 and $314,276 as of September 30, 2020 and December 31, 2019	401,197	583,262
Owned and leased mineral rights, net of accumulated depletion and amortization of $40,623 and $27,877 as of September 30, 2020 and December 31, 2019	489,631	523,141
Other acquired intangibles, net of accumulated amortization of $38,806 and $32,686 as of September 30, 2020 and December 31, 2019	100,350	125,145
Long-term restricted cash	124,065	122,524
Deferred income taxes	0	33,065
Other non-current assets	221,591	204,207
Total assets	1,923,123	2,302,823
Current liabilities:
Current portion of long-term debt	44,864	28,485
Trade accounts payable	75,836	98,746
Acquisition-related obligations – current	18,206	33,639
Accrued expenses and other current liabilities	153,372	154,282
Total current liabilities	292,278	315,152
Long-term debt	552,676	564,481
Acquisition-related obligations - long-term	19,286	46,259
Workers’ compensation and black lung obligations	263,517	260,778
Pension obligations	186,089	204,086
Asset retirement obligations	210,998	184,130
Deferred income taxes	368	422
Other non-current liabilities	54,943	31,393
Total liabilities	1,580,155	1,606,701
Commitments and Contingencies (Note 18)
Stockholders’ Equity
Preferred stock - par value $0.01, 5.0 million shares authorized, none issued	0	0
Common stock - par value $0.01, 50.0 million shares authorized, 20.6 million issued and 18.3 million outstanding at September 30, 2020 and 20.5 million issued and 18.2 million outstanding at December 31, 2019	206	205
Additional paid-in capital	778,728	775,707
Accumulated other comprehensive loss	(68,614)	(58,616)
Treasury stock, at cost: 2.3 million shares at September 30, 2020 and December 31, 2019	(106,976)	(107,984)
Retained (deficit) earnings	(260,376)	86,810
Total stockholders’ equity	342,968	696,122
Total liabilities and stockholders’ equity	$ 1,923,123	$ 2,302,823