Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Discontinued Operations, Disposed of by Means Other than Sale, Spinoff Knife River Corporation	Common Stock	Common Stock Discontinued Operations, Disposed of by Means Other than Sale, Spinoff Knife River Corporation	Other Paid-in Capital	Retained Earnings	Retained Earnings Discontinued Operations, Disposed of by Means Other than Sale, Spinoff Knife River Corporation	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Discontinued Operations, Disposed of by Means Other than Sale, Spinoff Knife River Corporation	Treasury Stock	Treasury Stock Discontinued Operations, Disposed of by Means Other than Sale, Spinoff Knife River Corporation
Common stock, beginning balance (in shares) at Dec. 31, 2022			204,162,814
Beginning balance at Dec. 31, 2022	$ 3,587,129		$ 204,163		$ 1,466,037	$ 1,951,138		$ (30,583)		$ (3,626)
Treasury stock, common, beginning balance (in shares) at Dec. 31, 2022										(538,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	38,353					38,353
Other comprehensive income (loss)	217							217
Dividends declared on common stock	(45,574)					(45,574)
Stock-based compensation	3,108				3,108
Repurchase of common stock (in shares)										(153,622)
Repurchase of common stock	(4,811)									$ (4,811)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)										153,622
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(3,040)				(7,851)					$ 4,811
Common stock, ending balance (in shares) at Mar. 31, 2023			204,162,814
Ending balance at Mar. 31, 2023	3,575,382		$ 204,163		1,461,294	1,943,917		(30,366)		$ (3,626)
Treasury stock, common, ending balance (in shares) at Mar. 31, 2023										(538,921)
Common stock, beginning balance (in shares) at Dec. 31, 2022			204,162,814
Beginning balance at Dec. 31, 2022	3,587,129		$ 204,163		1,466,037	1,951,138		(30,583)		$ (3,626)
Treasury stock, common, beginning balance (in shares) at Dec. 31, 2022										(538,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	243,974
Other comprehensive income (loss)	$ 518
Common stock, ending balance (in shares) at Sep. 30, 2023	203,638,373		203,638,373
Ending balance at Sep. 30, 2023	$ 2,757,434		$ 203,638		1,462,939	1,108,616		(17,759)		$ 0
Treasury stock, common, ending balance (in shares) at Sep. 30, 2023										0
Common stock, beginning balance (in shares) at Mar. 31, 2023			204,162,814
Beginning balance at Mar. 31, 2023	3,575,382		$ 204,163		1,461,294	1,943,917		(30,366)		$ (3,626)
Treasury stock, common, beginning balance (in shares) at Mar. 31, 2023										(538,921)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	130,692					130,692
Other comprehensive income (loss)	363							363
Dividends declared on common stock	(45,158)					(45,158)
Stock-based compensation	$ (927)				(927)
Separation of Knife River (in shares)				538,921							538,921
Separation of Knife River		$ (954,541)		$ (539)			$ (969,934)		$ 12,306		$ 3,626
Issuance of common stock (in shares)	14,480
Costs of issuance of common stock	$ 382		$ 14		368
Common stock, ending balance (in shares) at Jun. 30, 2023			203,638,373
Ending balance at Jun. 30, 2023	2,706,193		$ 203,638		1,460,735	1,059,517		(17,697)		$ 0
Treasury stock, common, ending balance (in shares) at Jun. 30, 2023										0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	74,929					74,929
Other comprehensive income (loss)	(62)							(62)
Dividends declared on common stock	(25,645)					(25,645)
Stock-based compensation	$ 2,204				2,204
Separation of Knife River		$ (185)					$ (185)
Common stock, ending balance (in shares) at Sep. 30, 2023	203,638,373		203,638,373
Ending balance at Sep. 30, 2023	$ 2,757,434		$ 203,638		1,462,939	1,108,616		(17,759)		$ 0
Treasury stock, common, ending balance (in shares) at Sep. 30, 2023										0
Common stock, beginning balance (in shares) at Dec. 31, 2023	203,689,090		203,689,090
Beginning balance at Dec. 31, 2023	$ 2,905,233		$ 203,689		1,466,235	1,253,693		(18,384)		$ 0
Treasury stock, common, beginning balance (in shares) at Dec. 31, 2023										0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	100,898					100,898
Other comprehensive income (loss)	74							74
Dividends declared on common stock	(25,779)					(25,779)
Stock-based compensation	3,173				3,173
Costs of issuance of common stock	(35)				(35)
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings (in shares)			199,147
Issuance of common stock upon vesting of stock-based compensation, net of shares used for tax withholdings	(2,623)		$ 199		(2,822)
Common stock, ending balance (in shares) at Mar. 31, 2024			203,888,237
Ending balance at Mar. 31, 2024	$ 2,980,941		$ 203,888		1,466,551	1,328,812		(18,310)		$ 0
Treasury stock, common, ending balance (in shares) at Mar. 31, 2024										0
Common stock, beginning balance (in shares) at Dec. 31, 2023	203,689,090		203,689,090
Beginning balance at Dec. 31, 2023	$ 2,905,233		$ 203,689		1,466,235	1,253,693		(18,384)		$ 0
Treasury stock, common, beginning balance (in shares) at Dec. 31, 2023										0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	225,950
Other comprehensive income (loss)	$ 497
Common stock, ending balance (in shares) at Sep. 30, 2024	203,888,237		203,888,237
Ending balance at Sep. 30, 2024	$ 3,057,985		$ 203,888		1,470,429	1,401,555		(17,887)		$ 0
Treasury stock, common, ending balance (in shares) at Sep. 30, 2024										0
Common stock, beginning balance (in shares) at Mar. 31, 2024			203,888,237
Beginning balance at Mar. 31, 2024	2,980,941		$ 203,888		1,466,551	1,328,812		(18,310)		$ 0
Treasury stock, common, beginning balance (in shares) at Mar. 31, 2024										0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	60,436					60,436
Other comprehensive income (loss)	139							139
Dividends declared on common stock	(25,644)					(25,644)
Stock-based compensation	1,947				1,947
Costs of issuance of common stock	(15)				(15)
Common stock, ending balance (in shares) at Jun. 30, 2024			203,888,237
Ending balance at Jun. 30, 2024	3,017,804		$ 203,888		1,468,483	1,363,604		(18,171)		$ 0
Treasury stock, common, ending balance (in shares) at Jun. 30, 2024										0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	64,615					64,615
Other comprehensive income (loss)	284							284
Dividends declared on common stock	(26,664)					(26,664)
Stock-based compensation	$ 1,946				1,946
Common stock, ending balance (in shares) at Sep. 30, 2024	203,888,237		203,888,237
Ending balance at Sep. 30, 2024	$ 3,057,985		$ 203,888		$ 1,470,429	$ 1,401,555		$ (17,887)		$ 0
Treasury stock, common, ending balance (in shares) at Sep. 30, 2024										0