Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidated Net Income			$ 2,529	$ 2,435	$ 2,031
Qualifying hedges:
Changes in fair value, net of tax			(136)	(13)	(10)
Reclassification adjustment for amounts included in net income, net of tax			69	6	5
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax			13	(2)	(51)
Reclassification adjustment for amounts included in net income, net of tax			4	7	3
Total other comprehensive income (loss)			(50)	(2)	(53)
Dividends on preferred and preference stock of subsidiaries			45	54	68
Comprehensive income attributable to noncontrolling interests			36	14	0
Comprehensive Income			2,398	2,365	1,910
Alabama Power [Member]
Consolidated Net Income			839	811	800
Qualifying hedges:
Changes in fair value, net of tax			(2)	(5)	(5)
Reclassification adjustment for amounts included in net income, net of tax			4	2	2
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			2	(3)	(3)
Dividends on preferred and preference stock of subsidiaries			17	26	39
Comprehensive Income			841	808	797
Georgia Power [Member]
Consolidated Net Income			1,347	1,277	1,242
Qualifying hedges:
Changes in fair value, net of tax			0	(9)	(5)
Reclassification adjustment for amounts included in net income, net of tax			2	2	2
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			2	(7)	(3)
Dividends on preferred and preference stock of subsidiaries			17	17	17
Comprehensive Income			1,349	1,270	1,239
Gulf Power [Member]
Consolidated Net Income			140	157	149
Qualifying hedges:
Changes in fair value, net of tax			1	1	0
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			1	1	0
Dividends on preferred and preference stock of subsidiaries			9	9	9
Comprehensive Income			141	158	149
Mississippi Power [Member]
Consolidated Net Income			(48)	(6)	(327)
Qualifying hedges:
Changes in fair value, net of tax			1	0	0
Reclassification adjustment for amounts included in net income, net of tax			1	1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			2	1	1
Dividends on preferred and preference stock of subsidiaries			2	2	2
Comprehensive Income			(46)	(5)	(326)
Southern Power [Member]
Consolidated Net Income			374	229	175
Qualifying hedges:
Changes in fair value, net of tax			(27)	0	0
Reclassification adjustment for amounts included in net income, net of tax			58	1	0
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			31	1	0
Comprehensive income attributable to noncontrolling interests			36	14	3
Comprehensive Income			$ 369	216	172
Successor [Member] | Southern Company Gas [Member]
Consolidated Net Income	$ 114
Qualifying hedges:
Changes in fair value, net of tax	(1)
Reclassification adjustment for amounts included in net income, net of tax	0
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax	27
Reclassification adjustment for amounts included in net income, net of tax	0
Total other comprehensive income (loss)	26
Comprehensive income attributable to noncontrolling interests	0
Comprehensive Income	$ 140
Predecessor [Member] | Southern Company Gas [Member]
Consolidated Net Income		$ 145		373	500
Qualifying hedges:
Changes in fair value, net of tax		(41)		0	(6)
Reclassification adjustment for amounts included in net income, net of tax		1		8	(3)
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax		0		0	(71)
Reclassification adjustment for amounts included in net income, net of tax		5		12	8
Total other comprehensive income (loss)		(35)		20	(72)
Comprehensive income attributable to noncontrolling interests		14		20	16
Comprehensive Income		$ 96		$ 373	$ 412