Regulatory Matters - GAS Narrative (Details) - Subsequent Event $ in Billions	Apr. 28, 2021 USD ($)	Apr. 06, 2021 mi
Virginia Natural Gas
Loss Contingencies [Line Items]
Motion filed to withdraw project application, header improvement project, scope of project | mi		9.5
Atlanta Gas Light
Loss Contingencies [Line Items]
Integrated capacity delivery plan, capital budgets and related operations and maintenance spending, term	10 years
Integrated capacity delivery plan, review period	5 months
Atlanta Gas Light | Minimum
Loss Contingencies [Line Items]
Integrated capacity delivery plan, capital forecast plan, amount, years one through three	$ 0.5
Atlanta Gas Light | Maximum
Loss Contingencies [Line Items]
Integrated capacity delivery plan, capital forecast plan, amount, years one through three	$ 0.6