Acquisitions and Dispositions - Assets Held for Sale (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets Held for Sale:
Current assets	$ 58	$ 393
Liabilities Held for Sale:
Current liabilities	36	425
Other non-current liabilities	39	2,836
SOUTHERN POWER CO
Liabilities Held for Sale:
Current liabilities	10	15
Disposal Group, Held-for-sale, Not Discontinued Operations
Assets Held for Sale:
Current assets	58	393
Total property, plant, and equipment	588	4,583
Goodwill and other intangible assets	51	40
Other non-current assets	46	727
Total Assets Held for Sale	743	5,743
Liabilities Held for Sale:
Current liabilities	36	425
Other non-current liabilities	39	932
Long-term debt		1,286
Accumulated deferred income taxes		618
Total Liabilities Held for Sale	75	3,261
Disposal Group, Held-for-sale, Not Discontinued Operations | SOUTHERN POWER CO
Assets Held for Sale:
Current assets	10	8
Total property, plant, and equipment	559	536
Goodwill and other intangible assets	40	40
Other non-current assets	0	0
Total Assets Held for Sale	609	584
Liabilities Held for Sale:
Current liabilities	10	15
Other non-current liabilities	0	0
Long-term debt		0
Accumulated deferred income taxes		0
Total Liabilities Held for Sale	$ 10	$ 15