Employee Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2023

Employee Benefit Plans [Abstract]

Schedule of Pension Plan and Other Benefits Plan

The Company uses a December 31 measurement date for all of its employee benefit plans. The tables below set forth information relating to the Company’s Pension Plan and Other Benefits Plan for 2023 and 2022.

	(Thousands of Dollars)
	Pension Plan						Other Benefits Plan
	Years Ended December 31,
	2023			2022			2023			2022
Change in Projected Benefit Obligation:
Beginning Balance	$	87,788		$	113,710		$	32,909		$	49,396
Service Cost		1,551			2,362			391			799
Interest Cost		4,270			3,042			1,608			1,325
Actuarial (Gain) Loss		1,966			(27,850	)		(5,968	)		(17,761	)
Benefits Paid		(3,722	)		(3,476	)		(940	)		(850	)
Ending Balance	$	91,853		$	87,788		$	28,000		$	32,909

Schedule of Change in Fair Value of Plan Assets

	(Thousands of Dollars)
	Pension Plan						Other Benefits Plan
	Years Ended December 31,
	2023			2022			2023			2022
Change in Fair Value of Plan Assets:
Beginning Balance	$	84,828		$	100,750		$	44,029		$	50,668
Actual Return on Plan Assets		10,840			(14,346	)		4,323			(6,639	)
Employer Contributions		400			1,900			940			850
Benefits Paid		(3,722	)		(3,476	)		(940	)		(850	)
Ending Balance	$	92,346		$	84,828		$	48,352		$	44,029
Funded Status	$	494		$	(2,960	)	$	20,352		$	11,120

Schedule of Employee Benefit Plans Recognized in Balance Sheet

	(Thousands of Dollars)
	Pension Plan					Other Benefits Plan
	As of December 31,
	2023			2022		2023			2022
Amounts Recognized in the Consolidated
Balance Sheets consist of:
Current Liability	$	933		$	529	$	—		$	—
Noncurrent Liability (Asset)		(1,427	)		2,431		(20,352	)		(11,120	)
Net Liability (Asset) Recognized	$	(494	)	$	2,960	$	(20,352	)	$	(11,120	)

Schedule of Components of Net Benefit Cost

	(Thousands of Dollars)
	Pension Plan									Other Benefits Plan
	Years Ended December 31,
	2023			2022			2021			2023			2022			2021
Components of Net Periodic Benefit Cost
Service Cost	$	1,551		$	2,362		$	2,696		$	391		$	799		$	917
Interest Cost		4,270			3,042			2,706			1,608			1,325			1,236
Expected Return on Plan Assets		(5,865	)		(7,041	)		(6,225	)		(3,082	)		(3,547	)		(3,142	)
Amortization of Net Actuarial Loss (Gain)		658			1,674			2,868			(191	)		—			527
Net Periodic Benefit Cost*	$	614		$	37		$	2,045		$	(1,274	)	$	(1,423	)	$	(462	)

*Service cost is included in Operations and Maintenance expense on the consolidated statements of income; all other amounts are included in Other Income (Expense), net.

Schedule of Regulatory Assets into Net Periodic Benefit Cost

Amounts that are expected to be amortized from Regulatory Assets into Net Periodic Benefit Cost in 2024 are as follows:

	(Thousands of Dollars)
	Pension Plan		Other Benefits Plan
Actuarial Loss (Gain)	$	153	$	(1,098	)

Schedule of Discount and Compensation Rates

The discount rate and compensation increase rate for determining our postretirement benefit plans’ benefit obligations and costs as of and for the years ended December 31, 2023, 2022 and 2021, respectively, are as follows:

	Pension Plan						Other Benefits Plan
	2023		2022		2021		2023		2022		2021
Weighted Average Assumptions:
Expected Return on Plan Assets		7.00%		7.00%		7.00%		7.00%		7.00%		7.00%
Discount Rate for:
Benefit Obligation		4.79%		4.98%		2.72%		4.79%		4.98%		2.72%
Benefit Cost		4.98%		2.72%		2.37%		4.98%		2.72%		2.37%
Compensation Increase for:
Benefit Obligation		3.00%		3.00%		3.00%		3.00%		3.00%		3.00%
Benefit Cost		3.00%		3.00%		3.00%		3.00%		3.00%		3.00%

Schedule of Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates

A one-percentage point change in assumed healthcare cost trend rates would have the following effects on the Other Benefits Plan:

	(Thousands of Dollars)
	1 Percentage Point
	Increase		Decrease
Effect on Current Year Service and Interest Costs	$	308	$	(246	)
Effect on Projected Benefit Obligation	$	3,264	$	(2,676	)

Schedule of Expected Benefit Payments

The following benefit payments, which reflect expected future service, are expected to be paid:

	(Thousands of Dollars)
Year	Pension Plan		Other Benefits Plan
2024	$	5,078	$	1,181
2025		5,457		1,310
2026		5,444		1,377
2027		5,522		1,417
2028		5,638		1,445
2029-2033		29,349		8,104
Totals	$	56,488	$	14,834

Schedule of Allocation of Plan Assets

The allocation of plan assets at December 31, 2023 and 2022 by asset category is as follows:

	Pension Plan						Other Benefits Plan
Asset Category	2023		2022		Target		2023		2022		Target
Equity Securities		58.1%		53.6%		55%		60.9%		55.2%		43%
Debt Securities		39.6%		40.9%		38%		36.1%		24.7%		50%
Cash		0.7%		3.9%		2%		3.0%		20.1%		2%
Real Estate/Commodities		1.6%		1.6%		5%		0.0%		0.0%		5%
Total		100.0%		100.0%				100.0%		100.0%

Schedule of Fair Value of Plan Assets

The following tables present Middlesex’s Pension Plan assets measured and recorded at fair value within the fair value hierarchy:

	(Thousands of Dollars)
	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
Mutual Funds	$	71,236	$	—	$	—	$	71,236
Money Market Funds		663		—		—		663
Common Equity Securities		12,544		—		—		12,544
Corporate Bonds		5,091		—		—		5,091
Agency/US Debt		1,854		—		—		1,854
Sovereign/Non-US Debt		958		—		—		958
Total Investments	$	92,346	$	—	$	—	$	92,346

	(Thousands of Dollars)
	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
Mutual Funds	$	71,559	$	—	$	—	$	71,559
Money Market Funds		3,271		—		—		3,271
Common Equity Securities		9,998		—		—		9,998
Total Investments	$	84,828	$	—	$	—	$	84,828

	(Thousands of Dollars)
	As of December 31, 2023
	Level 1		Level 2		Level 3		Total
Mutual Funds	$	29,437	$	—	$	—	$	29,437
Money Market Funds		1,429		—		—		1,429
Agency/US/State/Municipal Debt		—		17,486		—		17,486
Total Investments	$	30,866	$	17,486	$	—	$	48,352

	(Thousands of Dollars)
	As of December 31, 2022
	Level 1		Level 2		Level 3		Total
Mutual Funds	$	23,660	$	—	$	—	$	23,660
Money Market Funds		8,623		—		—		8,623
Agency/US/State/Municipal Debt		—		10,592		—		10,592
Other		1,154		—		—		1,154
Total Investments	$	33,437	$	10,592	$	—	$	44,029

Schedule of Table Presents Awarded But not Yet Vested Share

The following table presents awarded but not yet vested share information for the plan:

	Shares(thousands)			Unearned Compensation (thousands)			Weighted Average Granted Price
Balance, January 1, 2021		86		$	1,837
Granted		15			1,151		$	79.02
Vested		(18	)		—
Amortization of Compensation expense		—			(1,057	)
Balance, December 31, 2021		83			1,931
Granted		11			1,151		$	105.17
Vested		(17	)
Amortization of Compensation expense		—			(1,350	)
Balance, December 31, 2022		77			1,732
Granted		15			1,165		$	77.63
Vested		(18	)		—
Amortization of Compensation expense		—			(1,854	)
Balance, December 31, 2023		74		$	1,043