CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 238,438	$ 212,793
Trade accounts receivable, net of allowance for doubtful accounts of $793 and $0 as of June 30, 2020 and December 31, 2019	183,820	244,666
Inventories, net	143,198	162,659
Prepaid expenses and other current assets	122,354	91,361
Total current assets	687,810	711,479
Property, plant, and equipment, net of accumulated depreciation and amortization of $351,561 and $314,276 as of June 30, 2020 and December 31, 2019	423,367	583,262
Owned and leased mineral rights, net of accumulated depletion and amortization of $34,961 and $27,877 as of June 30, 2020 and December 31, 2019	495,303	523,141
Other acquired intangibles, net of accumulated amortization of $35,717 and $32,686 as of June 30, 2020 and December 31, 2019	103,439	125,145
Long-term restricted cash	109,930	122,524
Deferred income taxes	0	33,065
Other non-current assets	220,389	204,207
Total assets	2,040,238	2,302,823
Current liabilities:
Current portion of long-term debt	30,390	28,485
Trade accounts payable	70,027	98,746
Acquisition-related obligations – current	30,019	33,639
Accrued expenses and other current liabilities	161,453	154,282
Total current liabilities	291,889	315,152
Long-term debt	597,706	564,481
Acquisition-related obligations - long-term	18,283	46,259
Workers’ compensation and black lung obligations	266,390	260,778
Pension obligations	198,582	204,086
Asset retirement obligations	207,001	184,130
Deferred income taxes	389	422
Other non-current liabilities	50,583	31,393
Total liabilities	1,630,823	1,606,701
Commitments and Contingencies (Note 17)
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 June 30, 2020 and 20.5 million issued and 18.2 million outstanding at December 31, 2019	206	205
Additional paid-in capital	777,650	775,707
Accumulated other comprehensive loss	(69,747)	(58,616)
Treasury stock, at cost: 2.3 million shares at June 30, 2020 and December 31, 2019	(106,955)	(107,984)
Retained earnings	(191,739)	86,810
Total stockholders’ equity	409,415	696,122
Total liabilities and stockholders’ equity	$ 2,040,238	$ 2,302,823