Significant Accounting Policies - Earnings Per Share (Details) - $ / shares		12 Months Ended
	May 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted average common shares outstanding - basic (in shares)		203,867,000	203,640,000	203,358,000
Effect of dilutive performance share awards (in shares)		786,000	298,000	104,000
Weighted average common shares outstanding - diluted (in shares)		204,653,000	203,938,000	203,462,000
Earnings per share - basic:
Income from continuing operations (in usd per share)		$ 0.89	$ 1.62	$ 0.58
Discontinued operations, net of tax (in usd per share)		0.49	0.42	1.23
Earnings per share - basic (in usd per share)		1.38	2.04	1.81
Earnings per share - diluted:
Income from continuing operations (in usd per share)		0.88	1.62	0.58
Discontinued operations, net of tax (in usd per share)		0.49	0.41	1.23
Earnings per share - diluted (in usd per share)		$ 1.37	$ 2.03	$ 1.81
Shares excluded from the calculation of diluted earnings per share (in shares)		0	0	14,000
Dividends declared per common share (in usd per share)		$ 0.5100	$ 0.6950	$ 0.8750
Discontinued Operations, Disposed of by Means Other than Sale, Spinoff | Knife River Corporation
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Treasury stock, retired (in shares)	538,921