Property, Plant, and Equipment - Assets Acquired Under a Capital Lease (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Capital Leased Assets [Line Items]
Less: Accumulated amortization	$ (75)	$ (72)
Balance, net of amortization	191	201
Office buildings
Capital Leased Assets [Line Items]
Capital leased assets, gross	216	216
PPAs
Capital Leased Assets [Line Items]
Capital leased assets, gross	0	0
Computer-related equipment
Capital Leased Assets [Line Items]
Capital leased assets, gross	43	51
Gas pipeline
Capital Leased Assets [Line Items]
Capital leased assets, gross	7	6
Georgia Power
Capital Leased Assets [Line Items]
Less: Accumulated amortization	(84)	(68)
Balance, net of amortization	121	137
Georgia Power | Office buildings
Capital Leased Assets [Line Items]
Capital leased assets, gross	61	61
Georgia Power | PPAs
Capital Leased Assets [Line Items]
Capital leased assets, gross	144	144
Georgia Power | Computer-related equipment
Capital Leased Assets [Line Items]
Capital leased assets, gross	0	0
Georgia Power | Gas pipeline
Capital Leased Assets [Line Items]
Capital leased assets, gross	$ 0	$ 0