Consolidated Statement of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Operating activities:
Net income	$ 85,416	$ 61,036
Adjustments to reconcile net income to cash provided by operations:
Depreciation	82,035	66,860
Amortization	12,136	9,461
Deferred income taxes	28,054	8,844
Qualified defined benefit pension plan expense	5,437	2,164
Contributions to qualified defined benefit pension plans	(5,510)	(3,390)
Deferred environmental expenditures, net	(11,720)	(14,128)
Environmental remediation expense	8,549	8,075
Asset optimization revenue sharing bill credits	(15,549)	(29,198)
Other	7,794	7,322
Changes in assets and liabilities:
Receivables, net	121,551	118,562
Inventories	(4,382)	5,411
Income and other taxes	8,505	14,837
Accounts payable	11,582	(10,966)
Deferred gas costs	(45,247)	(14,418)
Asset optimization revenue sharing	(10,097)	(4,284)
Decoupling mechanism	(14,793)	4,085
Cloud-based software	(3,819)	(16,424)
Regulatory accounts	1,612	14,866
Other, net	22	8,793
Cash provided by operating activities	281,770	246,076
Investing activities:
Capital expenditures	(222,664)	(198,929)
Acquisitions, net of cash acquired	(331,329)	0
Purchase of equity method investment	(1,000)	(1,000)
Other	(894)	(512)
Cash used in investing activities	(555,887)	(200,441)
Financing activities:
Proceeds from common stock issued, net	24,384	34,986
Long-term debt issued	375,000	150,000
Long-term debt retired	(3,022)	(150,000)
Changes in other short-term debt, net	(17,692)	(10,780)
Cash dividend payments on common stock	(38,180)	(35,600)
Payment of financing fees	(4,385)	(748)
Shares withheld for tax purposes	(1,537)	(1,314)
Other	(1,769)	(764)
Cash used in financing activities	332,799	(14,220)
Cash, cash equivalents and restricted cash	106,664	81,039
Increase (decrease) in cash, cash equivalents and restricted cash	58,682	31,415
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	52,557	34,802
Income taxes paid, net of refunds	8,079	10,251
Northwest Natural Gas Company [Member]
Operating activities:
Net income	95,963	67,134
Adjustments to reconcile net income to cash provided by operations:
Depreciation	72,600	62,765
Amortization	11,327	9,241
Deferred income taxes	25,772	7,637
Qualified defined benefit pension plan expense	5,437	2,164
Contributions to qualified defined benefit pension plans	(5,510)	(3,390)
Deferred environmental expenditures, net	(11,720)	(14,128)
Environmental remediation expense	8,549	8,075
Asset optimization revenue sharing bill credits	(15,549)	(29,198)
Other	5,797	6,665
Changes in assets and liabilities:
Receivables, net	123,804	119,695
Inventories	(926)	5,629
Income and other taxes	13,977	3,971
Accounts payable	(2,512)	(13,544)
Deferred gas costs	(45,247)	(14,418)
Asset optimization revenue sharing	(10,097)	(4,284)
Decoupling mechanism	(14,793)	4,085
Cloud-based software	(3,819)	(16,424)
Regulatory accounts	1,638	14,867
Other, net	2,126	7,089
Cash provided by operating activities	277,011	232,199
Investing activities:
Capital expenditures	(177,122)	(179,015)
Other	(947)	(757)
Cash used in investing activities	(178,069)	(179,772)
Financing activities:
Capital contributions received from parent	135,000	0
Changes in other short-term debt, net	(136,510)	(16,780)
Cash dividend payments on common stock	(38,160)	(35,565)
Shares withheld for tax purposes	(1,537)	(1,314)
Other	(236)	(277)
Cash used in financing activities	(41,443)	(53,936)
Cash, cash equivalents and restricted cash	86,927	35,011
Increase (decrease) in cash, cash equivalents and restricted cash	57,499	(1,509)
Supplemental disclosure of cash flow information:
Interest paid, net of capitalization	28,718	28,735
Income taxes paid, net of refunds	$ 8,000	$ 24,920