Stockholders' Equity - Changes in Stockholders' Equity (Details) - USD ($) shares in Thousands, $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014	Jun. 30, 2015		Jun. 30, 2014
Changes in Stockholders' Equity
Beginning Balance					$ 20,926		$ 19,764
Net income after dividends on preferred and preference stock	[1]	$ 629	[2]	$ 611	1,138	[3]	962	[3]
Other comprehensive income (loss)					7		4
Treasury stock re-issued							216
Stock issued					117		161
Stock-based compensation					66
Stock repurchased, at cost					(115)		(5)
Cash dividends on common stock					(972)		(920)
Preference stock redemption					(150)
Contributions from noncontrolling interest					135
Distributions to noncontrolling interest					(5)
Net income attributable to noncontrolling interest					4
Other					(5)		0
Ending Balance		$ 21,146		$ 20,182	$ 21,146		$ 20,182
Number of Common shares Issued [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares					908,502		892,733
Stock issued, Shares					3,222		3,898
Ending Balance, Shares		911,724		896,631	911,724		896,631
Number of Common shares Treasury [Member]
Changes in Stockholders' Equity
Beginning Balance, Shares					725		5,647
Treasury stock re-issued, Shares							4,739
Stock repurchased, at cost, Shares					(2,599)
Other, Shares					25		(27)
Ending Balance, Shares		3,299		935	3,299		935
Common Stockholders' Equity [Member]
Changes in Stockholders' Equity
Beginning Balance					$ 19,949		$ 19,008
Net income after dividends on preferred and preference stock					1,138		962
Other comprehensive income (loss)					7		4
Treasury stock re-issued							216
Stock issued					117		161
Stock-based compensation					$ 66
Stock repurchased, at cost, Shares					(2,600)
Stock repurchased, at cost					$ (115)		(5)
Cash dividends on common stock					(972)		(920)
Other					(8)		0
Ending Balance		$ 20,182		$ 19,426	20,182		19,426
Preferred And Preference Stock [Member]
Changes in Stockholders' Equity
Beginning Balance					756		756
Stock issued							0
Preference stock redemption					(150)
Other					3
Ending Balance		609		$ 756	609		$ 756
Noncontrolling Interest [Member]
Changes in Stockholders' Equity
Beginning Balance	[4]				221
Contributions from noncontrolling interest	[4]				135
Distributions to noncontrolling interest	[4]				(5)
Net income attributable to noncontrolling interest	[4]				4
Ending Balance	[4]	$ 355			$ 355
Stock Option Exercises Through December 2017 [Member]
Changes in Stockholders' Equity
Stock repurchased, at cost, Shares					(20,000)

[1] After dividends on preferred and preference stock of subsidiaries.

[2] Segment net income (loss) for the traditional operating companies for the three months ended June 30, 2015 includes a $23 million pre-tax charge ($14 million after tax) for estimated probable losses on the Kemper IGCC. See Note (B) under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate" herein for additional information.

[3] Segment net income (loss) for the traditional operating companies for the six months ended June 30, 2015 and June 30, 2014 includes a $32 million pre-tax charge ($20 million after tax) and a $380 million pre-tax charge ($235 million after tax), respectively, for estimated probable losses on the Kemper IGCC. See Note (B) under "Integrated Coal Gasification Combined Cycle – Kemper IGCC Schedule and Cost Estimate" herein for additional information.

[4] Primarily related to Southern Power Company.