Consolidated Balance Sheets - USD ($) shares in Thousands, $ / shares in Thousands, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 30,168	$ 9,648
Accounts receivable	88,083	67,137
Accrued unbilled revenue	57,949	56,192
Allowance for uncollectible accounts	(3,219)	(673)
Regulatory assets	31,745	41,929
Derivative instruments	13,678	6,802
Inventories	42,691	43,985
Gas reserves	11,409	15,278
Income taxes receivable	6,000	256
Other current assets	44,741	38,004
Discontinued operations - current assets	0	15,134
Total current assets	323,245	293,692
Non-current assets:
Property, plant, and equipment	3,734,039	3,476,746
Less: Accumulated depreciation	1,079,269	1,037,847
Total property, plant, and equipment, net	2,654,770	2,438,899
Gas reserves	34,484	48,394
Regulatory assets	348,927	343,146
Derivative instruments	6,135	3,337
Other investments	49,259	63,333
Operating lease right of use asset	77,446	2,950
Assets under sales-type leases	143,759	146,310
Goodwill	69,225	49,929
Other non-current assets	49,129	38,464
Total non-current assets	3,433,134	3,134,762
Total assets	3,756,379	3,428,454
Current liabilities:
Short-term debt	304,525	149,100
Current maturities of long-term debt	95,344	75,109
Accounts payable	97,966	113,370
Taxes accrued	13,812	11,971
Interest accrued	7,441	7,451
Regulatory liabilities	50,362	44,657
Derivative instruments	4,198	2,000
Operating lease liabilities	1,105	2,101
Other current liabilities	52,330	62,705
Discontinued operations - current liabilities	0	13,709
Total current liabilities	627,083	482,173
Long-term debt	860,081	805,955
Deferred credits and other non-current liabilities:
Regulatory liabilities	639,663	625,717
Pension and other postretirement benefit liabilities	217,287	228,129
Derivative instruments	2,852	609
Operating lease liabilities	80,621	841
Other non-current liabilities	120,767	123,388
Total deferred credits and other non-current liabilities	1,380,482	1,274,327
Commitments and contingencies (see Note 17 and Note 18)
Equity:
Common stock - no par value	565,112	558,282
Retained earnings	336,523	318,450
Accumulated other comprehensive loss	(12,902)	(10,733)
Total equity	888,733	865,999
Total liabilities and equity	$ 3,756,379	$ 3,428,454
Par Value (in dollars per share)	$ 0	$ 0
Shares Authorized (in shares)	100,000	100,000
Shares issued (in shares)	30,589	30,472
Shares outstanding (in shares)	30,589	30,472
Deferred Income Tax Liabilities, Net	$ 319,292	$ 295,643
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	10,453	5,919
Accounts receivable	80,035	66,823
Accrued unbilled revenue	57,890	56,139
Receivables from affiliates	660	787
Allowance for uncollectible accounts	(3,107)	(672)
Regulatory assets	31,745	41,929
Derivative instruments	13,678	6,802
Inventories	42,325	43,896
Gas reserves	11,409	15,278
Other current assets	37,909	33,258
Total current assets	282,997	270,159
Non-current assets:
Property, plant, and equipment	3,683,776	3,456,075
Less: Accumulated depreciation	1,075,446	1,036,593
Total property, plant, and equipment, net	2,608,330	2,419,482
Gas reserves	34,484	48,394
Regulatory assets	348,887	343,146
Derivative instruments	6,135	3,337
Other investments	49,242	49,837
Operating lease right of use asset	77,328	2,760
Assets under sales-type leases	143,759	146,310
Other non-current assets	48,174	38,062
Total non-current assets	3,316,339	3,051,328
Total assets	3,599,336	3,321,487
Current liabilities:
Short-term debt	231,525	125,100
Current maturities of long-term debt	59,955	74,907
Accounts payable	95,170	111,641
Payables to affiliates	13,820	1,546
Taxes accrued	13,724	11,717
Interest accrued	7,338	7,441
Regulatory liabilities	50,362	44,657
Derivative instruments	4,198	2,000
Operating lease liabilities	1,054	1,979
Other current liabilities	51,907	61,438
Total current liabilities	529,053	442,426
Long-term debt	857,265	769,081
Deferred credits and other non-current liabilities:
Regulatory liabilities	638,793	625,717
Pension and other postretirement benefit liabilities	217,287	228,129
Derivative instruments	2,852	609
Operating lease liabilities	80,559	772
Other non-current liabilities	120,309	123,260
Total deferred credits and other non-current liabilities	1,377,834	1,287,784
Commitments and contingencies (see Note 17 and Note 18)
Equity:
Common stock - no par value	319,506	319,557
Retained earnings	528,580	513,372
Accumulated other comprehensive loss	(12,902)	(10,733)
Total equity	835,184	822,196
Total liabilities and equity	3,599,336	3,321,487
Deferred Income Tax Liabilities, Net	$ 318,034	$ 309,297