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 http://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 http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766

Debt and Financing Arrangements - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Jul. 25, 2018	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Line of Credit Facility [Line Items]
Weighted average interest rate on short term borrowings		1.40%	1.30%	1.20%
Capital lease obligation, current		$ 100,000
Capital lease obligation, noncurrent		200,000
Accounts Payable		39,000,000.0	$ 28,700,000	$ 52,400,000
Total rental expense under operating leases		500,000	500,000
Net Utility Plant		1,259,900,000	1,192,300,000	1,257,200,000
Guarantee outstanding		700,000
Operating lease obligations		500,000	$ 500,000
Other current operating lease obligation		1,600,000
Other noncurrent operating lease obligation		$ 3,200,000
Operating lease, weighted average remaining lease term		3 years 6 months	3 years 9 months 18 days
Operating lease, weighted average discount rate percentage		3.70%	4.20%
Guarantee Term Period		1 year
Assets under Capital Leases [Member]
Line of Credit Facility [Line Items]
Net Utility Plant		$ 600,000	$ 900,000	700,000
Net Utility Plant, accumulated amortization		$ 300,000	400,000	300,000
Northern Utilities Inc
Line of Credit Facility [Line Items]
Total funded indebtedness as percentage of capitalization		65.00%
Natural gas storage inventory		$ 2,000,000.0	1,500,000	8,300,000
Accounts Payable		1,500,000	500,000	1,600,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		120,000,000.0	$ 120,000,000.0	$ 120,000,000.0
Proceeds from lines of credit		96,800,000
Repayments of lines of credit		$ 96,900,000
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%