Revenue Recognition Disegragation of Revenue (Details) - USD ($)	3 Months Ended				9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018		Sep. 30, 2019		Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 92,626,000		$ 93,400,000		$ 347,630,000		$ 356,102,000
Revenue from Contract with Customer, Excluding Assessed Tax	92,626,000	[1]	93,400,000	[1]	347,630,000	[2]	356,102,000	[2]
Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	74,580,000	[1]	72,770,000	[1]	251,601,000	[2]	252,667,000	[2]
Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	22,279,000	[1]	24,423,000	[1]	108,985,000	[2]	115,778,000	[2]
Other Segments And Intersegments Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(4,233,000)		(3,793,000)		(12,956,000)		(12,343,000)
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(4,233,000)	[1]	(3,793,000)	[1]	(12,956,000)	[2]	(12,343,000)	[2]
Consolidation, Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(14,579,000)		(13,861,000)		(49,263,000)		(47,909,000)
Eliminations [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(9,487,000)		(7,359,000)		(28,200,000)		(25,362,000)
Other [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues	100,000		500,000		(100,000)		(400,000)
Other [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues	100,000		100,000		300,000		200,000
Revenue from Contract with Customer, Excluding Assessed Tax	(859,000)		(2,709,000)		(8,107,000)		(10,204,000)
Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	62,052,000		60,536,000		213,860,000		223,271,000
Energy Distribution [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	62,052,000		60,536,000		213,860,000		223,271,000
Energy Distribution [Member] | Delaware natural gas division [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,953,000		7,010,000		42,758,000		50,963,000
Energy Distribution [Member] | Delaware natural gas division [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,953,000		7,010,000		42,758,000		50,963,000
Energy Distribution [Member] | Central Florida Gas Division [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	6,710,000		6,282,000		21,625,000		18,462,000
Energy Distribution [Member] | Central Florida Gas Division [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax			6,282,000		21,625,000		18,462,000
Energy Distribution [Member] | FPU Electric Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	24,174,000		23,830,000		59,016,000		60,933,000
Energy Distribution [Member] | FPU Electric Distribution [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	24,174,000		23,830,000		59,016,000		60,933,000
Energy Distribution [Member] | Florida Public Utilities Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,908,000		17,390,000		60,357,000		58,885,000
Energy Distribution [Member] | Florida Public Utilities Company [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,908,000		17,390,000		60,357,000		58,885,000
Energy Distribution [Member] | Maryland Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,634,000		2,463,000		15,867,000		17,136,000
Energy Distribution [Member] | Maryland Natural Gas [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	2,634,000		2,463,000		15,867,000		17,136,000
Energy Distribution [Member] | Sandpiper [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,673,000		3,561,000		14,237,000		16,892,000
Energy Distribution [Member] | Sandpiper [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,673,000		3,561,000		14,237,000		16,892,000
Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	26,262,000		25,343,000		89,080,000		78,440,000
Energy Transmission [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	22,015,000		19,593,000		65,941,000		54,758,000
Energy Transmission [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,247,000		5,750,000		23,139,000		23,682,000
Energy Transmission [Member] | Aspire [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,247,000		5,750,000		23,139,000		23,682,000
Energy Transmission [Member] | Aspire [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,247,000		5,750,000		23,139,000		23,682,000
Energy Transmission [Member] | Eastern Shore Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,573,000		16,189,000		54,368,000		46,289,000
Energy Transmission [Member] | Eastern Shore Gas Company [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,573,000		16,189,000		54,368,000		46,289,000
Energy Transmission [Member] | Peninsula Pipeline [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,442,000		3,404,000		11,573,000		8,469,000
Energy Transmission [Member] | Peninsula Pipeline [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,442,000		3,404,000		11,573,000		8,469,000
Energy Generation [Member] | Eight Flags [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,027,000		4,044,000		12,405,000		12,652,000
Energy Generation [Member] | Eight Flags [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,027,000		4,044,000		12,405,000		12,652,000
Propane Delivery [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13,805,000		17,338,000		76,947,000		89,648,000
Propane Delivery [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	13,805,000		17,338,000		76,947,000		89,648,000
Energy Services [Member] | Marlin Gas Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,059,000				4,601,000		0
Energy Services [Member] | Marlin Gas Services [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,059,000				4,601,000		0
Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(15,108,000)		(14,472,000)		(50,928,000)		(49,905,000)
Eliminations [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(9,487,000)		(7,359,000)		(28,200,000)		(25,362,000)
Eliminations [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(1,254,000)		(3,185,000)		(9,377,000)		(11,679,000)
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	529,000		611,000		1,665,000		1,996,000
Other [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	395,000		476,000		1,270,000		1,475,000
Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 134,000		$ 135,000		$ 395,000		$ 521,000

[1] ⁽¹⁾ Total operating revenues for the three months ended September 30, 2019, include other revenue (revenues from sources other than contracts with customers) of $0.1 million and $0.1 million for our Regulated and Unregulated Energy segments, respectively, and $0.5 million and $0.1 million for our Regulated and Unregulated Energy segments, respectively, for the three months ended September 30, 2018. The sources of other revenues include revenue from alternative revenue programs related to revenue normalization for the Maryland division and Sandpiper and late fees.

[2] ⁽¹⁾ Total operating revenues for the nine months ended September 30, 2019, include other revenue (revenues from sources other than contracts with customers) of $(0.1) million and $0.3 million for our Regulated and Unregulated Energy segments, respectively, and $(0.4) million and $0.2 million for our Regulated and Unregulated Energy segments, respectively, for the nine months ended September 30, 2018. The sources of other revenues include revenue from alternative revenue programs related to revenue normalization for the Maryland division and Sandpiper and late fees.