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).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt and Financing Arrangements - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2022	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Line of Credit Facility [Line Items]
Weighted average interest rate on short term borrowings		3.60%	1.20%	2.40%	1.20%	1.20%
Capital lease obligation, current		$ 100,000		$ 100,000
Capital lease obligation, noncurrent		100,000		100,000
Accounts Payable		35,200,000	$ 29,500,000	35,200,000	$ 29,500,000	$ 52,400,000
Total rental expense under operating leases		500,000	500,000	1,400,000	1,400,000
Net Utility Plant		1,303,800,000	$ 1,237,300,000	1,303,800,000	1,237,300,000	1,257,200,000
Guarantee outstanding		1,600,000		1,600,000
Operating lease obligations				1,400,000	$ 1,400,000
Other current operating lease obligation		1,600,000		1,600,000
Other noncurrent operating lease obligation		$ 3,000,000		$ 3,000,000
Operating lease, weighted average remaining lease term		3 years 4 months 24 days	3 years 8 months 12 days	3 years 4 months 24 days	3 years 8 months 12 days
Operating lease, weighted average discount rate percentage		3.70%	4.00%	3.70%	4.00%
Guarantee Term Period				1 year
Assets under Capital Leases [Member]
Line of Credit Facility [Line Items]
Net Utility Plant		$ 600,000	$ 700,000	$ 600,000	$ 700,000	700,000
Net Utility Plant, accumulated amortization		$ 300,000	300,000	$ 300,000	300,000	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		$ 23,400,000	9,700,000	$ 23,400,000	9,700,000	8,300,000
Accounts Payable		300,000	100,000	300,000	100,000	1,600,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility		$ 200,000,000	$ 120,000,000	200,000,000	$ 120,000,000	$ 120,000,000
Proceeds from lines of credit				214,000,000
Repayments of lines of credit				$ 206,100,000
Credit Facility \| Third Amendment Credit Facility
Line of Credit Facility [Line Items]
Sublimit for the issuance of standby letters of credit	$ 25,000,000
Revolving credit facility	$ 200,000,000
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility expiration date	Sep. 29, 2027
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member]
Line of Credit Facility [Line Items]
Credit facility, daily fluctuating rate of interest	0.10%
Line of credit outstanding	$ 65,500,000
Line of credit interest rate during the period	4.272%
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member] \| Maximum [Member]
Line of Credit Facility [Line Items]
Credit facility, daily fluctuating rate of interest	1.375%
Debt instrument variable interest rate additional spread	1.375%
Credit Facility \| Revolving Credit Facility \| Third Amendment Credit Facility \| Secured Overnight Financing Rate [Member] \| Minimum [Member]
Line of Credit Facility [Line Items]
Credit facility, daily fluctuating rate of interest	1.125%
Debt instrument variable interest rate additional spread	1.125%