Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidated Net Income			$ 2,300	$ 926	$ 2,529
Qualifying hedges:
Changes in fair value, net of tax			(47)
Changes in fair value, net of tax				57	(136)
Reclassification adjustment for amounts included in net income, net of tax			72
Reclassification adjustment for amounts included in net income, net of tax				(60)	69
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax			(5)	17	13
Reclassification adjustment for amounts included in net income, net of tax			6	(23)	4
Total other comprehensive income (loss)			26	(9)	(50)
Dividends on preferred and preference stock of subsidiaries			16	38	45
Comprehensive income attributable to noncontrolling interests			58	46	36
Current period change			2,252	833	2,398
Alabama Power
Consolidated Net Income			945	866	839
Qualifying hedges:
Changes in fair value, net of tax			0
Changes in fair value, net of tax				1	(2)
Reclassification adjustment for amounts included in net income, net of tax			4
Reclassification adjustment for amounts included in net income, net of tax				3	4
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			4	4	2
Dividends on preferred and preference stock of subsidiaries			15	18	17
Current period change			949	870	841
Georgia Power
Consolidated Net Income			793	1,428	1,347
Qualifying hedges:
Reclassification adjustment for amounts included in net income, net of tax			3
Reclassification adjustment for amounts included in net income, net of tax				3	2
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			3	3	2
Dividends on preferred and preference stock of subsidiaries			0	14	17
Current period change			796	1,431	1,349
Mississippi Power
Consolidated Net Income			236	(2,588)	(48)
Qualifying hedges:
Changes in fair value, net of tax			(1)
Changes in fair value, net of tax				(1)	1
Reclassification adjustment for amounts included in net income, net of tax			1
Reclassification adjustment for amounts included in net income, net of tax				1	1
Pension and other postretirement benefit plans:
Total other comprehensive income (loss)			0	0	2
Dividends on preferred and preference stock of subsidiaries			1	2	2
Current period change			236	(2,588)	(46)
Southern Power
Consolidated Net Income			246	1,117	374
Qualifying hedges:
Changes in fair value, net of tax			(51)
Changes in fair value, net of tax				63	(27)
Reclassification adjustment for amounts included in net income, net of tax			58
Reclassification adjustment for amounts included in net income, net of tax				(73)	58
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax			5	0	0
Reclassification adjustment for amounts included in net income, net of tax			2	0	0
Total other comprehensive income (loss)			14	(10)	31
Comprehensive income attributable to noncontrolling interests			59	46	36
Current period change			201	1,061	$ 369
Southern Company Gas
Consolidated Net Income	$ 114		372	243
Qualifying hedges:
Changes in fair value, net of tax			5
Changes in fair value, net of tax	(1)			(5)
Reclassification adjustment for amounts included in net income, net of tax			(1)
Reclassification adjustment for amounts included in net income, net of tax	0			1
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax	27		0	(1)
Reclassification adjustment for amounts included in net income, net of tax	0		(2)	0
Total other comprehensive income (loss)	26		2	(5)
Comprehensive income attributable to noncontrolling interests	0		0	0
Current period change	$ 140		$ 374	$ 238
Predecessor | Southern Company Gas
Consolidated Net Income		$ 145
Qualifying hedges:
Changes in fair value, net of tax		(41)
Reclassification adjustment for amounts included in net income, net of tax		1
Pension and other postretirement benefit plans:
Benefit plan net gain (loss), net of tax		0
Reclassification adjustment for amounts included in net income, net of tax		5
Total other comprehensive income (loss)		(35)
Comprehensive income attributable to noncontrolling interests		14
Current period change		$ 96