Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 12,633	$ 3,472
Accounts receivable	66,970	66,236
Accrued unbilled revenue	57,827	62,381
Allowance for uncollectible accounts	(977)	(956)
Regulatory assets	41,930	45,781
Derivative instruments	9,001	1,735
Inventories	44,149	47,577
Gas reserves	16,647	15,704
Income taxes receivable	6,000	0
Other current assets	28,472	24,949
Discontinued operations - current assets	13,269	3,057
Total current assets	295,921	269,936
Non-current assets:
Property, plant, and equipment	3,414,490	3,204,635
Less: Accumulated depreciation	993,118	960,477
Total property, plant, and equipment, net	2,421,372	2,244,158
Gas reserves	66,197	84,053
Regulatory assets	371,786	356,608
Derivative instruments	725	1,306
Other investments	63,558	66,363
Goodwill	8,954	0
Other non-current assets	14,149	6,505
Discontinued operations - non-current assets	0	10,817
Total non-current assets	2,946,741	2,769,810
Total assets	3,242,662	3,039,746
Current liabilities:
Short-term debt	217,620	54,200
Current maturities of long-term debt	29,989	96,703
Accounts payable	115,878	111,021
Taxes accrued	11,023	18,883
Interest accrued	7,306	6,773
Regulatory liabilities	47,436	34,013
Derivative instruments	12,381	18,722
Other current liabilities	54,492	39,942
Discontinued operations - current liabilities	12,959	1,593
Total current liabilities	509,084	381,850
Long-term debt	706,247	683,184
Deferred credits and other non-current liabilities:
Deferred tax liabilities	280,463	270,526
Regulatory liabilities	611,560	586,093
Pension and other postretirement benefit liabilities	221,886	223,333
Derivative instruments	3,025	4,649
Discontinued operations - non-current liabilities		13,900
Other non-current liabilities	147,763	135,292
Discontinued operations - non-current liabilities	0	12,043
Total deferred credits and other non-current liabilities	1,264,697	1,231,936
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 28,880 and 28,736 at December 31, 2018 and 2017, respectively	457,640	448,865
Retained earnings	312,182	302,349
Accumulated other comprehensive loss	(7,188)	(8,438)
Total equity	762,634	742,776
Total liabilities and equity	3,242,662	3,039,746
Northwest Natural Gas Company [Member]
Current assets:
Cash and cash equivalents	7,947	3,110
Accounts receivable	66,824	66,236
Accrued unbilled revenue	57,773	62,381
Receivables from affiliates	4,166	266
Allowance for uncollectible accounts	(975)	(956)
Regulatory assets	41,930	45,781
Derivative instruments	9,001	1,735
Inventories	44,126	47,577
Gas reserves	16,647	15,704
Other current assets	25,347	24,862
Discontinued operations - current assets	0	7,170
Total current assets	272,786	273,866
Non-current assets:
Property, plant, and equipment	3,410,439	3,204,260
Less: Accumulated depreciation	992,855	960,285
Total property, plant, and equipment, net	2,417,584	2,243,975
Gas reserves	66,197	84,053
Regulatory assets	371,786	356,608
Derivative instruments	725	1,306
Other investments	49,922	52,654
Other non-current assets	13,736	6,505
Discontinued operations - non-current assets	0	24,709
Total non-current assets	2,919,950	2,769,810
Total assets	3,192,736	3,043,676
Current liabilities:
Short-term debt	217,500	54,200
Current maturities of long-term debt	29,989	96,703
Accounts payable	114,937	110,354
Payables to affiliates	523	3,664
Taxes accrued	10,990	18,844
Interest accrued	7,273	6,773
Regulatory liabilities	47,436	34,013
Derivative instruments	12,381	18,722
Other current liabilities	53,027	39,942
Discontinued operations - current liabilities	0	2,565
Total current liabilities	494,056	385,780
Long-term debt	704,134	683,184
Deferred credits and other non-current liabilities:
Deferred tax liabilities	294,739	287,388
Regulatory liabilities	611,560	586,093
Pension and other postretirement benefit liabilities	221,886	223,333
Derivative instruments	3,025	4,649
Discontinued operations - non-current liabilities	0	4,732
Other non-current liabilities	147,668	135,205
Total deferred credits and other non-current liabilities	1,278,878	1,231,936
Commitments and contingencies (see Note 16 and Note 17)
Equity:
Common stock - no par value; authorized 100,000 shares; issued and outstanding 28,880 and 28,736 at December 31, 2018 and 2017, respectively	226,452	448,865
Retained earnings	496,404	302,349
Accumulated other comprehensive loss	(7,188)	(8,438)
Total equity	715,668	742,776
Total liabilities and equity	$ 3,192,736	$ 3,043,676