Summary of Significant Accounting Policies - Asset Retirement Obligations (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	$ 1,757,000		$ 1,344,000
Liabilities incurred	6,000		45,000
Liabilities settled	(16,000)		(16,000)
Accretion	97,000		112,000
Cash flow revisions	174,000		272,000
Balance at end of year	2,018,000		1,757,000
Alabama Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	589,000		553,000
Liabilities incurred	0		0
Liabilities settled	(1,000)		(1,000)
Accretion	40,000		37,000
Cash flow revisions	102,000	[1]	0	[1]
Balance at end of year	730,000		589,000
Georgia Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	1,105,000		757,000
Liabilities incurred	2,000		24,000
Liabilities settled	(13,000)		(15,000)
Accretion	55,000		72,000
Cash flow revisions	73,000		267,000
Balance at end of year	1,222,000		1,105,000
Gulf Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	16,055		10,729
Liabilities incurred	518		0
Liabilities settled	(1,913)		(107)
Accretion	751		507
Cash flow revisions	773		4,926
Balance at end of year	16,184		16,055
Mississippi Power [Member]
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Balance at beginning of year	42,115		19,148
Liabilities incurred	0		20,989
Liabilities settled	(24)		(282)
Accretion	1,840		1,874
Cash flow revisions	(2,021)		386
Balance at end of year	$ 41,910		$ 42,115

[1] (a) Updated based on results from the 2013 nuclear decommissioning study