Financing Arrangements and Debt (Tables)

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Schedule of Long-term Debt

Long-term debt for the respective periods presented consisted of the following.

	December 31,
(Thousands of dollars)	2025		2024
Notes payable
5.875% notes, due December 2027	$	78,899	$	78,899
6.375% notes, due July 2028	148,590		148,590
7.050% notes, due May 2029	117,582		117,582
6.000% notes, due October 2032	600,000		600,000
5.875% notes, due December 2042 ¹	339,761		339,761
Total notes payable	1,284,832		1,284,832
Unamortized debt issuance cost and discount on notes payable	(12,406)		(14,336)
Total notes payable, net of unamortized discount	1,272,426		1,270,496
Finance lease obligations, due through November 2034	12,654		4,877
Total debt including current maturities	1,285,080		1,275,373
Senior Unsecured Revolving Credit Facility	100,000		—
Current maturities	(2,514)		(871)
Total long-term debt	$	1,382,566	$	1,274,502

1 Coupon rate may fluctuate 25 basis points if rating is periodically downgraded or upgraded by S&P and Moody’s.