Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities
Net income	$ 27,923	$ 230,347	$ 43,545
Adjustments to reconcile net income (loss) to net cash provided (used) by operating activities:
Deferred income taxes	5,366	36,854	(4,306)
Depreciation and amortization of property, plant and equipment	68,414	66,937	68,689
Amortization of intangible and other assets	508	1,082	1,254
(Gain) loss on extinguishments of debt	(8,644)	113	10,259
Amortization of debt issuance costs, including discounts and premiums	1,924	2,073	6,067
Stock-based compensation	5,353	4,025	5,516
Gain associated with commodity contracts			(2,706)
Other	1,160	(4,638)	2,653
Cash provided (used) by changes in assets and liabilities:
Accounts receivable	35,113	10,197	(42,913)
Inventories	2,755	(14,300)	3,261
Supplies, prepaid items and other	5,528	(8,548)	(8,642)
Accounts payable	(264)	18,821	932
Other assets and other liabilities	(7,615)	2,691	4,018
Net cash provided (used) by operating activities	137,521	345,654	87,627
Cash flows from investing activities
Expenditures for property, plant and equipment	(67,603)	(45,833)	(35,128)
Proceeds from short-term investments	389,856	158,879
Purchases of short-term investments	(264,448)	(486,091)
Other investing activities	(405)	3,310	434
Net cash provided (used) by investing activities	57,400	(369,735)	(34,694)
Cash flows from financing activities
Proceeds from revolving debt facilities			12,000
Payments on revolving debt facilities			(12,000)
Proceeds from 6.25% senior secured notes		200,000	500,000
Payments on other long-term debt	(9,536)	(13,750)	(10,472)
Payments of debt-related costs, including extinguishment costs	(94)	(4,840)	(27,254)
Proceeds from short-term financing	17,805	20,143	16,689
Payments on short-term financing	(20,542)	(16,725)	(17,549)
Acquisition of treasury stock, net	(28,305)	(174,975)
Taxes paid on equity awards	(2,666)	(4,012)	(4,228)
Payments of costs to exchange redeemable preferred stocks for common stock		(135)	(7,363)
Payments of dividends on non-redeemable preferred stocks			(1,876)
Net cash (used) provided by financing activities	(157,658)	5,706	12,947
Net increase (decrease) in cash and cash equivalents	37,263	(18,375)	65,880
Cash, cash equivalents and restricted cash at beginning of year	63,769	82,144	16,264
Cash, cash equivalents and restricted cash at end of year	101,032	$ 63,769	82,144
6.25% Senior Secured Notes due 2028 [Member]
Cash flows from financing activities
Repurchases or Payments on senior secured notes	$ (114,320)
9.625% Senior Secured Notes due 2023 [Member]
Cash flows from financing activities
Repurchases or Payments on senior secured notes			$ (435,000)