Introduction - Asset Retirement Obligations (Details) $ in Millions	9 Months Ended
	Sep. 30, 2016 USD ($)
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 3,759
Liabilities incurred	41
Liabilities settled	(117)
Accretion	119
Cash flow revisions	712
Balance at end of period	4,514
Alabama Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	1,448
Liabilities incurred	5
Liabilities settled	(12)
Accretion	55
Cash flow revisions	31
Balance at end of period	1,527
Georgia Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	1,916
Liabilities incurred	0
Liabilities settled	(93)
Accretion	56
Cash flow revisions	675
Balance at end of period	2,554
Gulf Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	130
Liabilities incurred	0
Liabilities settled	0
Accretion	2
Cash flow revisions	2
Balance at end of period	134
Mississippi Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	177
Liabilities incurred	15
Liabilities settled	(12)
Accretion	3
Cash flow revisions	7
Balance at end of period	190
Southern Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	21
Liabilities incurred	18
Liabilities settled	0
Accretion	1
Cash flow revisions	0
Balance at end of period	$ 40