CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 227,056	$ 212,793
Trade accounts receivable, net of allowance for doubtful accounts of $1,213 and $0 as of March 31, 2020 and December 31, 2019	245,377	244,666
Inventories, net	184,445	162,659
Prepaid expenses and other current assets	142,151	91,361
Total current assets	799,029	711,479
Property, plant, and equipment, net of accumulated depreciation and amortization of $349,444 and $314,276 as of March 31, 2020 and December 31, 2019	561,836	583,262
Owned and leased mineral rights, net of accumulated depletion and amortization of $33,590 and $27,877 as of March 31, 2020 and December 31, 2019	501,061	523,141
Other acquired intangibles, net of accumulated amortization of $34,631 and $32,686 as of March 31, 2020 and December 31, 2019	115,628	125,145
Long-term restricted cash	101,815	122,524
Deferred income taxes	0	33,065
Other non-current assets	212,548	204,207
Total assets	2,291,917	2,302,823
Current liabilities:
Current portion of long-term debt	29,529	28,485
Trade accounts payable	93,953	98,746
Acquisition-related obligations - current	33,211	33,639
Accrued expenses and other current liabilities	146,527	154,282
Total current liabilities	303,220	315,152
Long-term debt	623,474	564,481
Acquisition-related obligations - long-term	30,718	46,259
Workers’ compensation and black lung obligations	258,712	260,778
Pension obligations	204,605	204,086
Asset retirement obligations	189,459	184,130
Deferred income taxes	317	422
Other non-current liabilities	27,577	31,393
Total liabilities	1,638,082	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, 20.5 million issued and 18.3 million outstanding at March 31, 2020 and 20.5 million issued and 18.2 million outstanding at December 31, 2019	205	205
Additional paid-in capital	776,607	775,707
Accumulated other comprehensive loss	(62,626)	(58,616)
Treasury stock, at cost: 2.3 million shares at March 31, 2020 and December 31, 2019	(106,913)	(107,984)
Retained earnings	46,562	86,810
Total stockholders’ equity	653,835	696,122
Total liabilities and stockholders’ equity	$ 2,291,917	$ 2,302,823