Contingencies - GPC Litigation (Details) - Pending Litigation - Subsequent Event - Georgia Power - Municipal Franchise Fees Class Action	Feb. 13, 2019
Loss Contingencies [Line Items]
Stay period	60 days
Petition period	20 days

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.

No definition available.

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration