Income Tax (Tables)

12 Months Ended

Dec. 31, 2018

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The following table provides a reconciliation between income taxes calculated at the statutory federal tax rate and the provision for income taxes reflected in the NW Holdings and NW Natural statements of comprehensive income or loss for December 31:



	NW Holdings									NW Natural
Dollars in thousands	2018			2017			2016			2018			2017			2016
Income taxes at federal statutory rate	$	19,222		$	39,578		$	36,901		$	19,434		$	39,624		$	37,137
Increase (decrease):
State income tax, net of federal	4,927			5,066			4,844			4,982			5,072			4,858
Differences required to be flowed-through by regulatory commissions	1,302			2,357			2,357			1,302			2,357			2,357
Effect of the TCJA	—			(3,376		)	—			—			(2,956		)	—
Deferred tax rate differential post-TCJA	(76		)	—			—			(75		)	—			—
Other, net	(1,184		)	(2,617		)	(1,091		)	(1,184		)	(2,619		)	(1,077		)
Total provision for income taxes	$	24,191		$	41,008		$	43,011		$	24,459		$	41,478		$	43,275
Effective tax rate	26.4		%	36.3		%	40.8		%	26.4		%	36.6		%	40.8		%

Schedule of Components of Income Tax Expense (Benefit) [Table Text Block]

The provision for current and deferred income taxes consists of the following at December 31:



	NW Holdings						NW Natural
In thousands	2018		2017		2016		2018		2017		2016
Current
Federal	$	8,953	$	19,345	$	10,042	$	9,127	$	19,304	$	10,158
State	3,785		5,963		3,116		3,846		5,956		3,131
	12,738		25,308		13,158		12,973		25,260		13,289
Deferred
Federal	9,001		13,869		25,473		9,025		14,371		25,581
State	2,452		1,831		4,380		2,461		1,847		4,405
	11,453		15,700		29,853		11,486		16,218		29,986
Income tax provision	$	24,191	$	41,008	$	43,011	$	24,459	$	41,478	$	43,275

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]

The following table summarizes the tax effect of significant items comprising NW Holdings and NW Natural's deferred income tax balances recorded at December 31:



	NW Holdings				NW Natural
In thousands	2018		2017⁽¹⁾		2018		2017
Deferred tax liabilities:
Plant and property	$	288,385	$	278,735	$	303,186	$	296,113
Pension and postretirement obligations	27,135		23,352		27,135		23,352
Income tax regulatory asset	21,403		22,209		21,402		22,209
Other	1,061		2,766		537		2,250
Total deferred income tax liabilities	$	337,984	$	327,062	$	352,260	$	343,924
Deferred income tax assets:
Income tax regulatory liability	$	57,469	$	56,470	$	57,469	$	56,470
Alternative minimum tax credit carryforward	52		66		52		66
Total deferred income tax assets	$	57,521	$	56,536	$	57,521	$	56,536
Total net deferred income tax liabilities	$	280,463	$	270,526	$	294,739	$	287,388