Revenue Recognition Disaggregation of Revenue (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025		Dec. 31, 2024		Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Revenues	$ 930,000,000.0		$ 787,200,000		$ 670,600,000
Revenue from Contract with Customer, Excluding Assessed Tax	930,000,000.0	[1]	787,200,000	[2]	670,600,000	[3]
Other And Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(29,700,000)	[1]	(24,600,000)	[2]	(26,100,000)	[3]
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	200,000		200,000		200,000
Other [Member] | Segment Reporting, Reconciling Item, Corporate Nonsegment
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	200,000		200,000		200,000
Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	191,600,000		152,900,000		148,900,000
Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(117,300,000)		(91,400,000)		(85,700,000)
Eliminations [Member] | Consolidation, Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(29,900,000)		(24,800,000)		(26,300,000)
Regulated Energy
Disaggregation of Revenue [Line Items]
Revenues	687,800,000		583,400,000		473,600,000
Revenue from Contract with Customer, Excluding Assessed Tax	687,800,000	[1]	583,400,000	[2]	473,600,000	[3]
Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	633,800,000		532,000,000.0		421,000,000.0
Regulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	141,200,000		117,700,000		111,800,000
Regulated Energy | Eliminations [Member] | Consolidation, Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(87,200,000)		(66,300,000)		(59,200,000)
Unregulated Energy
Disaggregation of Revenue [Line Items]
Revenues	271,900,000		228,400,000		223,100,000
Revenue from Contract with Customer, Excluding Assessed Tax	271,900,000	[1]	228,400,000	[2]	223,100,000	[3]
Unregulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	50,400,000		35,200,000		37,100,000
Unregulated Energy | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	32,000,000.0		17,600,000
Unregulated Energy | Eliminations [Member] | Consolidation, Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(200,000)		(300,000)		(200,000)
Other [Member] | Regulated Energy
Disaggregation of Revenue [Line Items]
Revenues	800,000		1,600,000		1,200,000
Other [Member] | Unregulated Energy
Disaggregation of Revenue [Line Items]
Revenues	400,000				400,000
Florida Natural Gas Distribution [Member] | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax					168,400,000
Delaware natural gas division [Member] | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	103,500,000		76,900,000		83,900,000
FPU Electric Distribution [Member] | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	103,900,000		92,600,000		99,500,000
Florida Public Utilities Company [Member] | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	191,800,000		170,300,000
Maryland Natural Gas [Member] | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	64,200,000	[4]	51,900,000	[5]	57,100,000	[6]
Aspire [Member] | Unregulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	50,400,000		35,200,000		37,100,000
Eastern Shore Gas Company [Member] | Regulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	86,900,000		81,700,000		79,900,000
Peninsula Pipeline [Member] | Regulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	52,800,000		34,500,000		30,400,000
Eight Flags [Member] | Unregulated Energy | Energy Generation [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	18,100,000		18,000,000.0		19,200,000
Florida Propane [Member] | Unregulated Energy | Propane Delivery [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	171,600,000		157,900,000		154,700,000
Marlin Gas Services [Member] | Unregulated Energy | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	28,200,000		16,600,000		12,300,000
Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(117,100,000)		(91,200,000)		(85,500,000)
Eliminations [Member] | Other And Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(29,700,000)		(24,600,000)		(26,100,000)
Eliminations [Member] | Regulated Energy | Other And Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(87,200,000)		(66,300,000)		(59,200,000)
Eliminations [Member] | Unregulated Energy | Other And Intersegment Eliminations
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(200,000)		(300,000)		(200,000)
Aspire Energy Express | Regulated Energy | Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,500,000		1,500,000		1,500,000
Florida City Gas | Regulated Energy | Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	170,400,000		140,300,000		$ 12,100,000	[7]
Other RNG | Unregulated Energy | Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3,800,000		$ 1,000,000.0

[1] Total operating revenues for the year ended December 31, 2025, include other revenue (revenues from sources other than contracts with customers) of $0.8 million and $0.4 million for our Regulated and Unregulated Energy segments, respectively. The sources of other revenues include revenue from alternative revenue programs related to revenue normalization and late fees for the Maryland natural gas distribution businesses

[2] Total operating revenues for the year ended December 31, 2024, include other revenue (revenues from sources other than contracts with customers) of $1.6 million and $0.4 million for our Regulated and Unregulated Energy segments, respectively. The sources of other revenues include revenue from alternative revenue programs related to revenue normalization and late fees for the Maryland natural gas distribution businesses.

[3] (3) Total operating revenues for the year ended December 31, 2023, include other revenue (revenues from sources other than contracts with customers) of $1.2 million and $0.4 million for our Regulated and Unregulated Energy segments, respectively. The sources of other revenues include revenue from alternative revenue programs related to revenue normalization for Maryland division and Sandpiper and late fees

[4] (1) In accordance with the Maryland PSC approval of our natural gas base rate proceeding, effective April 2025, our natural gas distribution businesses in Maryland (Maryland natural gas division, Sandpiper Energy and Elkton Gas) are now consolidated for rate-making and other purposes and are reflected on a consolidated basis for all periods presented consistent with the final rate order. See Note 17, Rates and Other Regulatory Activities, for additional information.

[5] (1) In accordance with the Maryland PSC approval of our natural gas base rate proceeding, effective April 2025, our natural gas distribution businesses in Maryland (Maryland natural gas division, Sandpiper Energy and Elkton Gas) are now consolidated for rate-making and other purposes and are reflected on a consolidated basis for all periods presented consistent with the final rate order. See Note 17, Rates and Other Regulatory Activities, for additional information.

[6] (2) In accordance with the Maryland PSC approval of our natural gas base rate proceeding, effective April 2025, our natural gas distribution businesses in Maryland (Maryland natural gas division, Sandpiper Energy and Elkton Gas) are now consolidated for rate-making and other purposes and are reflected on a consolidated basis for all periods presented consistent with the final rate order. See Note 17, Rates and Other Regulatory Activities, for additional information.

[7] 1) Operating revenues for FCG include amounts from the acquisition date through December 31, 2023. For additional information on FCG's results, see Note 4, Acquisitions, and discussion under Item 7, Management's Discussion and Analysis of Financial Condition and Results of Operations.