Valuation Allowances and Reserves (Tables)

12 Months Ended

Dec. 31, 2018

Entity Information [Line Items]

Summary of Valuation Allowance

NORTHWEST NATURAL HOLDING COMPANY

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES

COLUMN A	COLUMN B		COLUMN C				COLUMN D		COLUMN E
			Additions				Deductions
In thousands (year ended December 31)	Balance at beginning of period		Charged to costs and expenses		Charged to other accounts		Net write-offs		Balance at end of period
2018
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	956	$	680	$	—	$	659	$	977
2017
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	1,290	$	865	$	—	$	1,199	$	956
2016
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	870	$	1,246	$	—	$	826	$	1,290

Northwest Natural Gas Company [Member]

Entity Information [Line Items]

Summary of Valuation Allowance

NORTHWEST NATURAL GAS COMPANY

SCHEDULE II - VALUATION AND QUALIFYING ACCOUNTS AND RESERVES

COLUMN A	COLUMN B		COLUMN C				COLUMN D		COLUMN E
			Additions				Deductions
In thousands (year ended December 31)	Balance at beginning of period		Charged to costs and expenses		Charged to other accounts		Net write-offs		Balance at end of period
2018
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	956	$	678	$	—	$	659	$	975
2017
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	1,290	$	865	$	—	$	1,199	$	956
2016
Reserves deducted in balance sheet from assets to which they apply:
Allowance for uncollectible accounts	$	870	$	1,246	$	—	$	826	$	1,290