Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-in Capital:	Retained Earnings:	Derivative Financial Instruments	Deferred Retirement Benefit Costs	Accumulated Other Comprehensive Loss:	Total Shareholders’ Equity	Noncontrolling Interests:	Union Electric Company	Union Electric Company Common Stock	Union Electric Company Other Paid-in Capital:	Union Electric Company Preferred Stock	Union Electric Company Retained Earnings:	Ameren Illinois Company	Ameren Illinois Company Common Stock	Ameren Illinois Company Other Paid-in Capital:	Ameren Illinois Company Preferred Stock	Ameren Illinois Company Retained Earnings:
Beginning of period at Dec. 31, 2023			$ 7,216	$ 4,136	$ 0	$ (6)			$ 129			$ 2,725		$ 3,647					$ 3,756
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			30
Stock-based compensation activity			18
Capital contributions from parent										$ 350		350
Net income	$ 979									537					$ 454
Net Income Available to Common Shareholder				975											453
Dividends on common stock				(535)										0					(50)
Dividends on preferred stock														(3)					(1)
Change in derivative financial instruments					0
Change in deferred retirement benefit costs	(4)					(4)
Net income attributable to noncontrolling interest holders	$ (4)								4
Dividends paid to noncontrolling interest holders									(4)
Common stock shares outstanding at beginning of period at Dec. 31, 2023	266,300,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	400,000
Shares issued for stock-based compensation	200,000
Common stock shares outstanding at end of period at Sep. 30, 2024	266,900,000
End of period at Sep. 30, 2024	$ 11,962	$ 3	7,264	4,576	0	(10)	$ (10)		129		$ 511	3,075	$ 80	4,181		$ 0	$ 3,020	$ 49	4,159
Shareholders' equity, end of year at Sep. 30, 2024								$ 11,833		7,847					7,228
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 2.01
Beginning of period at Jun. 30, 2024			7,246	4,299	0	(9)			129			3,075		3,800					4,070
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			9
Stock-based compensation activity			9
Capital contributions from parent												0
Net income	$ 457									382					114
Net Income Available to Common Shareholder				456											114
Dividends on common stock				(179)										0					(25)
Dividends on preferred stock														(1)					0
Change in derivative financial instruments					0
Change in deferred retirement benefit costs	(1)					(1)
Net income attributable to noncontrolling interest holders	$ (1)								1
Dividends paid to noncontrolling interest holders									(1)
Common stock shares outstanding at beginning of period at Jun. 30, 2024	266,800,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation	0
Common stock shares outstanding at end of period at Sep. 30, 2024	266,900,000
End of period at Sep. 30, 2024	$ 11,962	3	7,264	4,576	0	(10)	(10)		129		511	3,075	80	4,181		0	3,020	49	4,159
Shareholders' equity, end of year at Sep. 30, 2024								11,833		$ 7,847					$ 7,228
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 0.67
Beginning of period at Dec. 31, 2024	$ 12,243		7,513	4,604	3	(9)			129			3,201		4,206					4,266
Common stock shares outstanding at beginning of period at Dec. 31, 2024	269,900,000									102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued for stock-based compensation	300,000
Common stock shares outstanding at end of period at Jun. 30, 2025	270,400,000
End of period at Jun. 30, 2025			7,541	4,784	(3)	(11)			129			3,201		4,348					4,564
Beginning of period at Dec. 31, 2024	$ 12,243		7,513	4,604	3	(9)			129			3,201		4,206					4,266
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			35
Stock-based compensation activity			11
Capital contributions from parent										$ 0		0
Net income	1,208									$ 713					$ 522
Net Income Available to Common Shareholder				1,204											$ 521
Dividends on common stock				(576)										(125)					(185)
Dividends on preferred stock														(3)					(1)
Change in derivative financial instruments					(6)
Change in deferred retirement benefit costs	(2)					(2)
Net income attributable to noncontrolling interest holders	$ (4)								4
Dividends paid to noncontrolling interest holders									(4)
Common stock shares outstanding at beginning of period at Dec. 31, 2024	269,900,000									102,100,000					25,500,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	300,000
Shares issued for stock-based compensation	300,000
Common stock shares outstanding at end of period at Sep. 30, 2025	270,500,000									102,100,000					25,500,000
End of period at Sep. 30, 2025	$ 12,909	3	7,559	5,232	(3)	(11)	(14)		129		511	3,201	80	4,791		0	3,056	49	4,602
Shareholders' equity, end of year at Sep. 30, 2025	$ 12,780							12,780		$ 8,583					$ 7,707
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 2.13
Beginning of period at Jun. 30, 2025			7,541	4,784	(3)	(11)			129			3,201		4,348					4,564
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan			10
Stock-based compensation activity			8
Capital contributions from parent												0
Net income	$ 641									$ 519					148
Net Income Available to Common Shareholder				640											$ 148
Dividends on common stock				(192)										(75)					(110)
Dividends on preferred stock														(1)					0
Change in derivative financial instruments					0
Change in deferred retirement benefit costs	0					0
Net income attributable to noncontrolling interest holders	$ (1)								1
Dividends paid to noncontrolling interest holders									(1)
Common stock shares outstanding at beginning of period at Jun. 30, 2025	270,400,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under the DRPlus and 401(k) plan	100,000
Shares issued for stock-based compensation	0
Common stock shares outstanding at end of period at Sep. 30, 2025	270,500,000									102,100,000					25,500,000
End of period at Sep. 30, 2025	$ 12,909	$ 3	$ 7,559	$ 5,232	$ (3)	$ (11)	$ (14)		$ 129		$ 511	$ 3,201	$ 80	$ 4,791		$ 0	$ 3,056	$ 49	$ 4,602
Shareholders' equity, end of year at Sep. 30, 2025	$ 12,780							$ 12,780		$ 8,583					$ 7,707
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends per common share	$ 0.71

AMEREN CORP 10-Q