Revenue Recognition Disegragation of Revenue (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 130,903,000		$ 136,664,000		$ 358,519,000		$ 376,020,000
Revenue from Contract with Customer, Excluding Assessed Tax	130,903,000	[1]	136,664,000	[1]	358,519,000	[2]	376,020,000	[2]
Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	73,403,000	[1]	70,504,000	[1]	177,021,000	[2]	179,897,000	[2]
Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	66,904,000	[1]	76,345,000	[1]	205,007,000	[2]	221,712,000	[2]
Other Segments And Intersegments Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(9,404,000)		(10,185,000)		(23,509,000)		(25,589,000)
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(9,404,000)	[1]	(10,185,000)	[1]	(23,509,000)	[2]	(25,589,000)	[2]
Consolidation, Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(20,530,000)		(23,104,000)		(49,471,000)		(51,087,000)
Eliminations [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(8,968,000)		(10,176,000)		(18,714,000)		(18,003,000)
Other [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues	(300,000)		(400,000)		(200,000)		(900,000)
Other [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenues	100,000		100,000		200,000		200,000
Revenue from Contract with Customer, Excluding Assessed Tax	(2,158,000)		(2,743,000)		(7,248,000)		(7,495,000)
Energy Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	61,066,000		63,210,000		151,808,000		162,735,000
Energy Distribution [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	61,066,000		63,210,000		151,808,000		162,735,000
Energy Distribution [Member] | Delaware natural gas division [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	8,256,000		11,882,000		35,805,000		43,954,000
Energy Distribution [Member] | Delaware natural gas division [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	8,256,000		11,882,000		35,805,000		43,954,000
Energy Distribution [Member] | Central Florida Gas Division [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	7,015,000		6,317,000		14,915,000		12,180,000
Energy Distribution [Member] | Central Florida Gas Division [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	7,015,000		6,317,000		14,915,000		12,180,000
Energy Distribution [Member] | FPU Electric Distribution [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	20,464,000		18,362,000		34,842,000		37,103,000
Energy Distribution [Member] | FPU Electric Distribution [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	20,464,000		18,362,000		34,842,000		37,103,000
Energy Distribution [Member] | Florida Public Utilities Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	18,663,000		18,281,000		42,449,000		41,494,000
Energy Distribution [Member] | Florida Public Utilities Company [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	18,663,000		18,281,000		42,449,000		41,494,000
Energy Distribution [Member] | Maryland Natural Gas [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,186,000		4,001,000		13,233,000		14,673,000
Energy Distribution [Member] | Maryland Natural Gas [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,186,000		4,001,000		13,233,000		14,673,000
Energy Distribution [Member] | Sandpiper [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,482,000		4,367,000		10,564,000		13,331,000
Energy Distribution [Member] | Sandpiper [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,482,000		4,367,000		10,564,000		13,331,000
Energy Transmission [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	26,726,000		23,324,000		62,819,000		53,096,000
Energy Transmission [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	21,305,000		17,470,000		43,927,000		35,165,000
Energy Transmission [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,421,000		5,854,000		18,892,000		17,931,000
Energy Transmission [Member] | Aspire [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,421,000		5,854,000		18,892,000		17,931,000
Energy Transmission [Member] | Aspire [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	5,421,000		5,854,000		18,892,000		17,931,000
Energy Transmission [Member] | Eastern Shore Gas Company [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,740,000		14,502,000		36,796,000		30,100,000
Energy Transmission [Member] | Eastern Shore Gas Company [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,740,000		14,502,000		36,796,000		30,100,000
Energy Transmission [Member] | Peninsula Pipeline [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,565,000		2,968,000		7,131,000		5,065,000
Energy Transmission [Member] | Peninsula Pipeline [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	3,565,000		2,968,000		7,131,000		5,065,000
Energy Generation [Member] | Eight Flags [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,235,000		4,230,000		8,377,000		8,608,000
Energy Generation [Member] | Eight Flags [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	4,235,000		4,230,000		8,377,000		8,608,000
Propane Delivery [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,018,000		20,206,000		63,143,000		72,311,000
Propane Delivery [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	17,018,000		20,206,000		63,143,000		72,311,000
Energy Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	42,388,000		48,798,000		121,843,000		130,357,000
Energy Services [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	42,388,000		48,798,000		121,843,000		130,357,000
Energy Services [Member] | Marlin Gas Services [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,108,000				3,541,000		0
Energy Services [Member] | Marlin Gas Services [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	1,108,000				3,541,000		0
Energy Services [Member] | PESCO [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41,280,000		48,798,000		118,302,000		130,357,000
Energy Services [Member] | PESCO [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	41,280,000		48,798,000		118,302,000		130,357,000
Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(21,132,000)		(23,803,000)		(50,610,000)		(52,473,000)
Eliminations [Member] | Regulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(8,968,000)		(10,176,000)		(18,714,000)		(18,003,000)
Eliminations [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(2,628,000)		(3,248,000)		(8,123,000)		(8,494,000)
Eliminations [Member] | Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	(9,536,000)		(10,379,000)		(23,773,000)		(25,976,000)
Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	602,000		699,000		1,139,000		1,386,000
Other [Member] | Unregulated Energy [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	470,000		505,000		875,000		999,000
Other [Member] | Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 132,000		$ 194,000		$ 264,000		$ 387,000

[1] ⁽¹⁾ Total operating revenues for the three months ended June 30, 2019, include other revenue (revenues from sources other than contracts with customers) of $(0.3) million and $0.1 million for our Regulated and Unregulated Energy segments, respectively, and $(0.4) million and $0.1 million for our Regulated and Unregulated Energy segments, respectively, for the three months ended June 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 six months ended June 30, 2019, include other revenue (revenues from sources other than contracts with customers) of $(0.2) million and $0.2 million for our Regulated and Unregulated Energy segments, respectively, and $(0.9) million and $0.2 million for our Regulated and Unregulated Energy segments, respectively, for the six months ended June 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.