v3.10.0.1
Summary of Significant Accounting Policies - Provision for Uncollectible Accounts (Narrative) (Details)
12 Months Ended
Dec. 31, 2018
Accounting Policies [Abstract]
Uncollectible accounts, average percent of revenues (less than)
1.00%
X
- Definition
Uncollectible accounts
+ References
No definition available.
+ Details
Name:
so_UncollectibleAccounts
Namespace Prefix:
so_
Data Type:
num:percentItemType
Balance Type:
na
Period Type:
duration
X
- References
No definition available.
+ Details
Name:
us-gaap_AccountingPoliciesAbstract
Namespace Prefix:
us-gaap_
Data Type:
xbrli:stringItemType
Balance Type:
na
Period Type:
duration