CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 88,450	$ 122,892
Trade accounts receivable	18,894	15,444
Accounts receivable from affiliates	4,764	6,411
Inventories	47,551	40,465
Refundable federal income taxes	17,615	8,928
Prepaid expenses and other	10,872	6,528
Total current assets	188,146	200,668
Property, plant and equipment, net	172,417	138,061
Intangibles, net	35,330	37,902
Investment in unconsolidated subsidiaries	28,978	24,611
Operating lease right-of-use assets	10,324	11,398
Other non-current assets	40,984	32,133
Total assets	476,179	444,773
Current liabilities
Accounts payable	5,522	9,374
Accounts payable to affiliates	125	577
Revolving credit agreements	20,000	7,000
Current portion of borrowings outstanding	2,112	795
Asset retirement obligations	1,844	2,285
Accrued payroll	14,430	19,583
Deferred compensation	0	13,465
Other current liabilities	8,224	8,887
Total current liabilities	52,257	61,966
Long-term debt	24,353	17,148
Operating lease liabilities	11,196	12,448
Asset retirement obligations	39,888	34,574
Pension and other postretirement obligations	8,838	8,807
Deferred income taxes	17,550	12,338
Liability for uncertain tax positions	9,413	1,912
Other long-term liabilities	12,060	6,188
Total liabilities	175,555	155,381
Common stock:
Capital in excess of par value	10,895	8,911
Retained earnings	294,270	284,852
Accumulated other comprehensive loss	(11,599)	(11,337)
Total stockholders’ equity	300,624	289,392
Total liabilities and equity	476,179	444,773
Class A Common Stock
Common stock:
Common stock	5,490	5,397
Class B Common Stock
Common stock:
Common stock	$ 1,568	$ 1,569