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Increase in volume of natural gas customer is under contract to purchase after specified events have occurred.

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Represents the number of long term gas contracts.

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Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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For an unclassified balance sheet, the amount of fees and other revenue, excluding investment income receivable, earned but not yet received, which were recognized in conformity with revenue recognition criteria based on estimates or specific contractual terms.

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The net amount of operating interest income (expense).

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Amount awarded from other party in judgment or settlement of litigation.

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No definition available.

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Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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No definition available.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

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Cash received for the settlement of litigation during the current period.

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Amount, including tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value-added and excise.

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All taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.

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Contingencies (Details)				1 Months Ended		2 Months Ended	3 Months Ended			4 Months Ended		9 Months Ended
Contingencies (Details)	Jun. 20, 2019 USD ($)	Feb. 01, 2018 MMBTU / d	Jan. 01, 2018 MMBTU / d	Oct. 29, 2019 USD ($)	Jul. 31, 2017 MMBTU / d	Jan. 31, 2018 MMBTU / d	Sep. 30, 2019 USD ($) contract	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Oct. 29, 2019 USD ($)	Nov. 30, 2017 MMBTU / d	Sep. 30, 2019 USD ($) MMBTU / d contract	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Nov. 30, 2018 MMBTU / d	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)
Contingencies
Revenues from contracts with customers							$ 896,612,000	$ 1,019,555,000				$ 2,980,757,000	$ 2,865,104,000
Production and ad valorem taxes							28,863,000	30,518,000				95,509,000	82,232,000
Interest							(47,754,000)	(74,528,000)				(173,868,000)	(208,303,000)
Accrued revenue							281,177,000					281,177,000		$ 474,827,000
Accounts receivable							29,207,000					29,207,000		$ 51,073,000
Natural gas sales
Contingencies
Revenues from contracts with customers							524,448,000	$ 527,122,000				$ 1,735,086,000	$ 1,498,324,000
Doddridge County, Tyler County and Ritchie County, West Virginia \| Minimum
Contingencies
Settlement amount									$ 100,000
SJGC
Contingencies
Natural gas long term purchase contract volume (in MMBtu)/day \| MMBTU / d												80,000
SJGC \| Settled Litigation
Contingencies
Settlement amount received				$ 23,000,000			59,000,000			$ 82,000,000
Production and ad valorem taxes							3,000,000					$ 3,000,000
Interest							8,000,000					8,000,000
Accrued revenue							23,000,000					23,000,000
SJGC \| Settled Litigation \| Natural gas sales
Contingencies
Revenues from contracts with customers							$ 54,000,000					$ 54,000,000
WGL
Contingencies
Natural gas long term purchase contract volume increase after specified events (in MMBtu)/day \| MMBTU / d															530,000
Damages awarded	$ 96,000,000
WGL \| Pending Litigation
Contingencies
Damages sought																$ 40,000,000
WGL \| Pending Litigation \| Minimum
Contingencies
Damages sought																	$ 30,000,000
WGL - Braxton, West Virginia
Contingencies
Natural gas long term purchase contract volume (in MMBtu)/day \| MMBTU / d		200,000	500,000
WGL - Loudoun County, Virginia
Contingencies
Natural gas long term purchase contract volume increase after specified events (in MMBtu)/day \| MMBTU / d															330,000
Potential Positive Outcome of Litigation \| SJGC
Contingencies
Number of long term gas contracts \| contract							2					2
Potential Positive Outcome of Litigation \| WGL
Contingencies
Natural gas long term purchase contract volume (in MMBtu)/day \| MMBTU / d					500,000	500,000					600,000