Other Investments (Narrative) (Details) - RGC Midstream LLC [Member] Bcf in Millions, $ in Millions	1 Months Ended
	Apr. 30, 2018 USD ($) mi	Mar. 31, 2020 USD ($) debt_instrument	Nov. 30, 2019	Jun. 12, 2019 instrument_held	Oct. 31, 2015 Bcf
Schedule of Equity Method Investments [Line Items]
Number of unsecured Promissory Notes funding the investment		2		2
MVP [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest percentage			1.03%		1.00%
Pipeline capacity per day (in bcf) | Bcf					2
MVP [Member] | Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Total project cost		$ 5,300.0
Total estimated investment		55.0
MVP [Member] | Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Total project cost		5,500.0
Total estimated investment		$ 57.0
Southgate [Member]
Schedule of Equity Method Investments [Line Items]
Length of planned natural gas pipeline (in miles) | mi	74
Estimated total MVP Southgate pipeline cost projection	$ 500.0
Estimated investment in MVP Southgate	$ 2.5
Southgate [Member] | Southgate [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage (less than)	1.00%