Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022
Operating activities:
Net income		$ 281,108		$ 414,707		$ 367,489
Income from discontinued operations, net of tax		100,035		84,590		250,237
Income from continuing operations		181,073		330,117		117,252
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		200,078		190,450		188,560
Deferred income taxes		(16,078)		(1,309)		20,187
Provision for credit losses		6,558		7,422		5,409
Amortization of debt issuance costs		1,828		1,013		885
Employee stock-based compensation costs		8,423		5,505		7,913
Pension and postretirement benefit plan net periodic benefit credit		(3,837)		(5,380)		(7,323)
Unrealized (gains) losses on investments		(5,942)		(7,431)		10,119
(Gains) losses on sales of assets		(857)		(347)		15
Gain on tax-free exchange of the retained shares in Knife River		0		(186,556)		0
Changes in current assets and liabilities, net of acquisitions:
Receivables		(30,310)		79,111		(91,193)
Inventories		246		(21,729)		243
Other current assets		80,977		(48,492)		14,522
Accounts payable		(443)		(87,209)		84,547
Other current liabilities		(5,252)		73,365		(26,873)
Pension and postretirement benefit plan contributions		(3,000)		(7,643)		(81)
Other noncurrent changes		(1,651)		(15,554)		(2,567)
Net cash provided by continuing operations		411,813		305,333		321,615
Net cash provided by discontinued operations		90,505		27,294		188,449
Net cash provided by operating activities		502,318		332,627		510,064
Investing activities:
Capital expenditures		(522,824)		(484,136)		(442,582)
Net proceeds from sale or disposition of property		691		260		3
Cost of removal, net of salvage value		(5,539)		1,170		(11,779)
Investments		(5,155)		(2,423)		(2,571)
Proceeds from investment cost basis withdrawal		9,000		20,000		0
Net cash used in continuing operations		(523,827)		(465,129)		(456,929)
Net cash used in discontinued operations		(28,858)		(75,662)		(181,952)
Net cash used in investing activities		(552,685)		(540,791)		(638,881)
Financing activities:
Issuance of short-term borrowings		0		810,000		11,500
Repayment of short-term borrowings		(95,000)		(433,901)		0
Issuance of long-term debt		308,600		594,700		214,969
Repayment of long-term debt		(182,135)		(568,883)		(38,764)
Debt issuance costs		(2,456)		(2,521)		(1,129)
Costs of issuance of common stock		(50)		0		(150)
Dividends paid		(102,939)		(161,316)		(176,915)
Repurchase of common stock		0		(4,811)		(7,399)
Tax withholding on stock-based compensation		(2,623)		(3,040)		(4,904)
Net cash (used in) provided by continuing operations		(76,603)		230,228		(2,792)
Net cash provided by (used in) discontinued operations		116,899		(25,606)		157,965
Net cash provided by financing activities		40,296		204,622		155,173
(Decrease) increase in cash, cash equivalents and restricted cash		(10,071)		(3,542)		26,356
Cash, cash equivalents and restricted cash - beginning of year		76,975	[1]	80,517	[1]	54,161
Cash, cash equivalents and restricted cash - end of year	[1]	$ 66,904		$ 76,975		$ 80,517

[1] *Includes cash of discontinued operations of $16.5 million and $9.7 million for the years ended December 31, 2023 and 2022, respectively.