Discontinued Operations (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 21, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Federal Statutory Income Tax Rate, Percent	21.00%												35.00%
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Discontinued operations - current assets	$ 3,057	$ 13,269				$ 3,057					$ 13,269	$ 3,057
Discontinued operations - non-current assets	10,817	0				10,817					0	10,817		$ 210,400
Discontinued operations - total assets	13,900					13,900						13,900
Discontinued operations - current liabilities	1,593	12,959				1,593					12,959	1,593
Discontinued operations - non-current liabilities	12,043	0				12,043					0	12,043
Discontinued Operation, Income Statement Disclosures [Abstract]
Loss from discontinued operations, net of tax		$ (959)	$ (650)	$ (659)	$ (474)	$ (124,655)	$ (608)	$ (1,346)	$ (1,087)		$ (2,742)	$ (127,696)		$ (3,524)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.02)	$ (4.34)	$ (0.02)	$ (0.04)	$ (0.04)		$ (0.10)	$ (4.45)		$ (0.13)
Diluted (in dollars per share)		$ (0.03)	$ (0.02)	$ (0.02)	$ (0.02)	$ (4.33)	$ (0.02)	$ (0.04)	$ (0.04)		$ (0.09)	$ (4.44)		$ (0.13)
Gill Ranch [Member] | Discontinued Operations, Held-for-sale or Disposed of by Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Accounts receivable	2,126	$ 390				$ 2,126					$ 390	$ 2,126
Inventories	396	685				396					685	396
Other current assets	535	333				535					333	535
Property, plant, and equipment	10,816	11,621				10,816					11,621	10,816
Less: Accumulated depreciation	0	7				0					7	0
Other non-current assets	1	247				1					247	1
Discontinued operations - current assets	3,057	13,269				3,057					13,269	3,057
Discontinued operations - non-current assets	10,817	0				10,817					0	10,817
Discontinued operations - total assets	13,874	13,269				13,874					13,269	13,874
Accounts payable	1,287	873				1,287					873	1,287
Other current liabilities	306	307				306					307	306
Other non-current liabilities	12,043	11,779				12,043					11,779	12,043
Discontinued operations - current liabilities	1,593	12,959				1,593					12,959	1,593
Discontinued operations - non-current liabilities	12,043	0				12,043					0	12,043
Total discontinued operations liabilities	13,636	$ 12,959				13,636					12,959	13,636
Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues											3,579	7,135		$ 7,794
Operations and maintenance											5,771	7,245		6,643
General taxes											479	1,373		1,295
Depreciation and amortization											430	4,525		4,685
Other expenses and interest											609	975		992
Impairment expense											0	192,478		0
Total expenses											7,289	206,596		13,615
Loss from discontinued operations before income tax											(3,710)	(199,461)		(5,821)
Income tax benefit											(968)	(71,765)		(2,297)
Loss from discontinued operations, net of tax											$ (2,742)	$ (127,696)		$ (3,524)
Loss from discontinued operations per share of common stock
Basic (in dollars per share)											$ (0.10)	$ (4.45)		$ (0.13)
Diluted (in dollars per share)											$ (0.09)	$ (4.44)		$ (0.13)
Transferred Subsidiaries - NW Natural Discontinued Operations [Member] | Discontinued Operations, Disposed of by Means Other than Sale [Member]
Disposal Group, Including Discontinued Operation, Classified Balance Sheet Disclosures [Abstract]
Cash	362					362						$ 362
Accounts receivable	2,126					2,126						2,126
Intercompany receivables	3,664					3,664						3,664
Inventories	396					396						396
Other current assets	622					622						622
Property, plant, and equipment	11,191					11,191						11,191
Less: Accumulated depreciation	192					192						192
Other investments	13,710					13,710						13,710
Other non-current assets	0					0						0
Discontinued operations - current assets	7,170					7,170						7,170
Discontinued operations - non-current assets	24,709					24,709						24,709
Discontinued operations - total assets	31,879					31,879						31,879
Accounts payable	1,954					1,954						1,954
Intercompany payables	266					266						266
Other current liabilities	345					345						345
Deferred tax liabilities	(16,862)					(16,862)						(16,862)
Other non-current liabilities	12,130					12,130						12,130
Discontinued operations - current liabilities	2,565					2,565						2,565
Discontinued Operation, Liabilities, Noncurrent	(4,732)					(4,732)						(4,732)
Total discontinued operations liabilities	$ (2,167)					$ (2,167)						(2,167)
Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues											$ 3,016	7,360		$ 8,018
Operations and maintenance											4,151	7,423		7,387
General taxes											448	1,410		1,317
Depreciation and amortization											420	4,555		4,714
Other expenses and interest											342	650		1,097
Impairment expense											0	192,478		0
Total expenses											5,361	206,516		14,515
Loss from discontinued operations before income tax											(2,345)	(199,156)		(6,497)
Income tax benefit											(622)	(71,813)		(2,557)
Loss from discontinued operations, net of tax											$ (1,723)	(127,343)		$ (3,940)
Gill Ranch [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership		75.00%									75.00%
Pacific Gas and Electric Company [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percent ownership		25.00%									25.00%
Scenario, Forecast [Member] | Minimum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses										$ 25,000
Scenario, Forecast [Member] | Maximum [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses										$ 26,500
TCJA Revaluation [Member] | Gill Ranch [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax benefit												18,000
TCJA Revaluation [Member] | Transferred Subsidiaries - NW Natural Discontinued Operations [Member] | Discontinued Operations, Held-for-sale [Member]
Discontinued Operation, Income Statement Disclosures [Abstract]
Income tax benefit												$ 18,000