Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Operating activities:
Net income	$ 63,823	$ 71,671
Adjustments to reconcile net income to cash provided by operations:
Depreciation	33,098	31,465
Regulatory amortization of gas reserves	546	833
Deferred income taxes	8,041	5,228
Qualified defined benefit pension plan expense (benefit)	1,082	(791)
Deferred environmental expenditures, net	(6,264)	(4,113)
Environmental remediation expense	5,746	5,375
Asset optimization revenue sharing bill credits	(20,608)	(10,471)
Other	8,905	8,509
Changes in assets and liabilities:
Receivables, net	17,839	38,727
Inventories	13,070	46,129
Income and other taxes	21,796	25,567
Accounts payable	(30,930)	(47,773)
Deferred gas costs	(8,808)	(11,300)
Increase (Decrease) in Asset Optimization Revenue Sharing	108	(7,769)
Decoupling mechanism	6,427	(1,303)
Change in Cloud-based software Assets	(6,485)	(3,673)
Asset optimization revenue sharing	13,335	958
Other, net	4,534	14,054
Cash provided by operating activities	125,039	176,861
Investing activities:
Payments to Acquire Property, Plant, and Equipment	(82,217)	(71,265)
Acquisitions, net of cash acquired	0	(468)
Purchase of equity method investment	(1,000)	0
Other	729	(1,285)
Cash used in investing activities	(82,488)	(73,018)
Financing activities:
Proceeds from common stock issued, net	12,218	16,669
Long-term debt issued	150,000	200,000
Long-term debt retired	(150,000)	0
Changes in other short-term debt, net	4,920	(185,700)
Cash dividend payments on common stock	(17,746)	(16,532)
Payment of financing fees	(748)	(1,498)
Shares withheld for tax purposes	(1,314)	(1,312)
Other	(247)	(440)
Cash used in financing activities	(2,917)	11,187
Cash, cash equivalents and restricted cash	89,258	155,994
Increase (decrease) in cash, cash equivalents and restricted cash	39,634	115,030
Supplemental disclosure of cash flow information:
Income taxes paid, net of refunds	1,000	1,300
Interest paid, net of capitalization	18,044	14,904
Northwest Natural Gas Company [Member]
Operating activities:
Net income	67,558	75,540
Adjustments to reconcile net income to cash provided by operations:
Depreciation	31,107	30,144
Regulatory amortization of gas reserves	546	833
Deferred income taxes	6,624	6,495
Qualified defined benefit pension plan expense (benefit)	1,082	(791)
Deferred environmental expenditures, net	(6,264)	(4,113)
Environmental remediation expense	5,746	5,375
Asset optimization revenue sharing bill credits	(20,608)	(10,471)
Other	8,189	7,851
Changes in assets and liabilities:
Receivables, net	17,636	36,671
Inventories	13,249	46,509
Income and other taxes	15,279	20,310
Accounts payable	(31,563)	(48,531)
Deferred gas costs	(8,808)	(11,299)
Increase (Decrease) in Asset Optimization Revenue Sharing	108	(7,769)
Decoupling mechanism	6,427	(1,303)
Change in Cloud-based software Assets	(6,485)	(3,673)
Asset optimization revenue sharing	13,335	958
Other, net	5,041	16,557
Cash provided by operating activities	117,983	174,831
Investing activities:
Payments to Acquire Property, Plant, and Equipment	(72,037)	(63,598)
Other	483	(1,284)
Cash used in investing activities	(71,554)	(64,882)
Financing activities:
Capital contributions from parent	0	8
Long-term debt issued	0	200,000
Changes in other short-term debt, net	14,920	(170,200)
Cash dividend payments on common stock	(17,694)	(16,552)
Shares withheld for tax purposes	(1,314)	(1,312)
Other	(97)	(1,660)
Cash used in financing activities	(4,185)	10,284
Cash, cash equivalents and restricted cash	78,764	144,904
Increase (decrease) in cash, cash equivalents and restricted cash	42,244	120,233
Supplemental disclosure of cash flow information:
Income taxes paid, net of refunds	8,670	6,565
Interest paid, net of capitalization	$ 14,104	$ 10,522