Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2020

Components of Gas and Electric Operating Revenue

In the following tables, revenue is classified by the types of goods/services rendered and market/customer type.

	Twelve Months Ended December 31, 2020
Gas and Electric Operating Revenues (millions):	Gas			Electric		Total
Billed and Unbilled Revenue:
Residential	$	73.1		$	128.7	$	201.8
Commercial & Industrial		104.5			91.4		195.9
Other		7.6			6.6		14.2
Total Billed and Unbilled Revenue		185.2			226.7		411.9
Rate Adjustment Mechanism Revenue		6.2			0.5		6.7
Total Gas and Electric Operating Revenues	$	191.4		$	227.2	$	418.6
	Twelve Months Ended December 31, 2019
Gas and Electric Operating Revenues (millions):	Gas			Electric		Total
Billed and Unbilled Revenue:
Residential	$	81.4		$	121.5	$	202.9
Commercial & Industrial		120.1			93.8		213.9
Other		10.6			7.8		18.4
Total Billed and Unbilled Revenue		212.1			223.1		435.2
Rate Adjustment Mechanism Revenue		(8.7	)		10.8		2.1
Total Gas and Electric Operating Revenues	$	203.4		$	233.9	$	437.3

	Twelve Months Ended December 31, 2018
Gas and Electric Operating Revenues (millions):	Gas		Electric			Total
Billed and Unbilled Revenue:
Residential	$	81.4	$	123.6		$	205.0
Commercial & Industrial		119.7		96.4			216.1
Other		9.6		8.7			18.3
Total Billed and Unbilled Revenue		210.7		228.7			439.4
Rate Adjustment Mechanism Revenue		5.4		(5.4	)		—
Total Gas and Electric Operating Revenues	$	216.1	$	223.3		$	439.4

Components of Accrued Revenue

Accrued Revenue (millions)	December 31,
	2020		2019
Regulatory Assets—Current	$	37.3	$	35.8
Unbilled Revenues		13.6		14.2
Total Accrued Revenue	$	50.9	$	50.0

Components of Exchange Gas Receivable

Exchange Gas Receivable (millions)	December 31,
	2020		2019
Northern Utilities	$	4.4	$	5.5
Fitchburg		0.5		0.6
Total Exchange Gas Receivable	$	4.9	$	6.1

Components of Gas Inventory

The following table shows the components of Gas Inventory as of December 31, 2020 and 2019.

Gas Inventory (millions)	December 31,
	2020		2019
Natural Gas	$	0.2	$	0.4
Propane		0.3		0.3
Liquefied Natural Gas & Other		0.1		0.1
Total Gas Inventory	$	0.6	$	0.8

Regulatory Assets

Regulatory Assets consist of the following (millions)	December 31,
	2020		2019
Retirement Benefits	$	103.7	$	88.9
Energy Supply & Other Rate Adjustment Mechanisms		34.1		31.0
Deferred Storm Charges		4.1		5.6
Environmental		5.2		7.2
Income Taxes		3.4		4.2
Other Deferred Charges		14.2		10.9
Total Regulatory Assets		164.7		147.8
Less: Current Portion of Regulatory Assets(1)		37.3		35.8
Regulatory Assets—noncurrent	$	127.4	$	112.0

(1)  Reflects amounts included in the Accrued Revenue on the Company’s Consolidated Balance Sheets.

Regulatory Liabilities

Regulatory Liabilities consist of the following (millions)	December 31,
	2020		2019
Rate Adjustment Mechanisms	$	4.1	$	6.0
Income Taxes		45.5		47.6
Other		0.2		0.4
Total Regulatory Liabilities		49.8		54.0
Less: Current Portion of Regulatory Liabilities		5.5		7.4
Regulatory Liabilities—noncurrent	$	44.3	$	46.6

Fair Value of Marketable Securities

Fair Value of Marketable Securities (millions)	December 31,
	2020		2019
Money Market Funds	$	5.7	$	5.6
Total Marketable Securities	$	5.7	$	5.6

Components of Energy Supply Obligations

	December 31,
Energy Supply Obligations consist of the following: (millions)	2020		2019
Current:
Exchange Gas Obligation	$	4.4	$	5.5
Renewable Energy Portfolio Standards		5.7		4.7
Power Supply Contract Divestitures		0.3		0.3
Total Energy Supply Obligations—Current		10.4		10.5
Noncurrent:
Power Supply Contract Divestitures		—		0.3
Total Energy Supply Obligations	$	10.4	$	10.8

Deferred Compensation Plan [Member]

Components of Energy Supply Obligations

Fair Value of Marketable Securities (millions)	December 31,
	2020		2019
Equity Funds	$	0.2	$	0.1
Money Market Funds		0.3		0.1
Total Marketable Securities	$	0.5	$	0.2