Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(a))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 852
-SubTopic 10
-Section 55
-Paragraph 10
-URI https://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Debt and Financing Arrangements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 25, 2018	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Line of Credit Facility [Line Items]
Weighted average interest rate on short term borrowings		2.10%	1.20%	1.70%	1.30%	1.20%
Capital lease obligation, current		$ 100,000		$ 100,000
Capital lease obligation, noncurrent		100,000		100,000
Accounts Payable		34,300,000	$ 32,600,000	34,300,000	$ 32,600,000	$ 52,400,000
Total rental expense under operating leases		500,000	500,000	900,000	1,000,000
Net Utility Plant		1,279,100,000	$ 1,209,800,000	1,279,100,000	1,209,800,000	1,257,200,000
Guarantee outstanding		700,000		700,000
Operating lease obligations				900,000	$ 1,000,000
Other current operating lease obligation		1,500,000		1,500,000
Other noncurrent operating lease obligation		$ 2,900,000		$ 2,900,000
Operating lease, weighted average remaining lease term		3 years 3 months 18 days	3 years 7 months 6 days	3 years 3 months 18 days	3 years 7 months 6 days
Operating lease, weighted average discount rate percentage		3.60%	4.20%	3.60%	4.20%
Guarantee Term Period				1 year
Assets under Capital Leases [Member]
Line of Credit Facility [Line Items]
Net Utility Plant		$ 700,000	$ 900,000	$ 700,000	$ 900,000	700,000
Net Utility Plant, accumulated amortization		$ 400,000	500,000	$ 400,000	500,000	300,000
Northern Utilities Inc
Line of Credit Facility [Line Items]
Total funded indebtedness as percentage of capitalization		65.00%		65.00%
Natural gas storage inventory		$ 12,600,000	4,900,000	$ 12,600,000	4,900,000	8,300,000
Accounts Payable		200,000	100,000	200,000	100,000	1,600,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		$ 120,000,000	$ 120,000,000	120,000,000	$ 120,000,000	$ 120,000,000
Proceeds from lines of credit				151,900,000
Repayments of lines of credit				$ 169,800,000
Credit Facility \| Second Amended Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility	$ 120,000,000
Sublimit for the issuance of standby letters of credit	$ 25,000,000
Credit Facility \| Second Amended Credit Facility \| London Interbank Offered Rate
Line of Credit Facility [Line Items]
Credit facility, daily fluctuating rate of interest	1.125%