Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Northwest Natural Gas Company [Member]	Common Stock Including APIC [Member]	Common Stock Including APIC [Member] Northwest Natural Gas Company [Member]	Retained Earnings [Member]	Retained Earnings [Member] Northwest Natural Gas Company [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Northwest Natural Gas Company [Member]
Beginning Balance at Dec. 31, 2022	$ 1,175,441	$ 1,191,082	$ 805,253	$ 614,903	$ 376,473	$ 582,593	$ (6,285)	$ (6,414)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		8		8
Net income	71,671	75,540			71,671	75,540
Dividends on common stock					(17,547)	(16,552)
Other comprehensive income (loss)	71,362	75,642					(309)	102
Stock-based compensation			2,580
Shares issued pursuant to equity based plans, net of shares withheld for taxes			(174)
Issuances of common stock, net of issuance costs			16,645
Ending Balance at Mar. 31, 2023	$ 1,248,307	1,250,180	824,304	614,911	430,597	641,581	(6,594)	(6,312)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4850
Beginning Balance at Dec. 31, 2023	$ 1,283,838	1,232,620	890,976	644,903	399,911	594,954	(7,049)	(7,237)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital contributions from parent		0		0
Net income	63,823	67,558			63,823	67,558
Dividends on common stock					(18,676)	(17,694)
Other comprehensive income (loss)	64,047	67,436					224	(122)
Stock-based compensation			1,728
Shares issued pursuant to equity based plans, net of shares withheld for taxes			231
Issuances of common stock, net of issuance costs			12,218
Ending Balance at Mar. 31, 2024	$ 1,343,386	$ 1,282,362	$ 905,153	$ 644,903	$ 445,058	$ 644,818	$ (6,825)	$ (7,359)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per share of common stock	$ 0.4875