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 Income (Loss)	Total Ameren Corporation Stockholders' Equity	Noncontrolling Interest	Ameren Missouri	Ameren Missouri Common Stock	Ameren Missouri Other Paid-In Capital	Ameren Missouri Preferred Stock Not Subject To Mandatory Redemption	Ameren Missouri Retained Earnings	Ameren Illinois	Ameren Illinois Common Stock	Ameren Illinois Other Paid-In Capital	Ameren Illinois Preferred Stock Not Subject To Mandatory Redemption	Ameren Illinois Retained Earnings
Common Stock at Dec. 31, 2021			$ 6,502	$ 3,182	$ 0	$ 13			$ 129			$ 2,725		$ 2,595			$ 2,914		$ 2,677
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Value, New Issues			292
Shares issued under the DRPlus and 401(k) plan			49
Stock-based compensation activity			17
Capital contribution from parent										$ 0		0			$ 15		15
Net income	$ 1,079													565					515
Net Income (Loss) Available to Common Stockholders, Basic	1,074			1,074						562					513
Common stock dividends				(610)										(46)					0
Preferred stock dividends														(3)					(2)
Change in derivative financial instruments					0
Change in deferred retirement benefit costs	(14)					(14)
Net income attributable to noncontrolling interest holders	$ (5)								5
Dividends paid to noncontrolling interest holders									(5)
Beginning of year (shares) at Dec. 31, 2021	257,700,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock Issued During Period, Shares, New Issues	3,400,000
Shares issued under the DRPlus and 401(k) plan	500,000
Shares issued (in shares)	400,000
End of year (shares) at Dec. 31, 2022	262,000,000.0
End of year at Dec. 31, 2022	$ 10,637	$ 3	6,860	3,646	0	(1)	$ (1)		129		$ 511	2,725	$ 80	3,111		$ 0	2,929	$ 49	3,190
Stockholders' equity, end of year at Dec. 31, 2022								$ 10,508		6,427					6,168
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.36
Stock Issued During Period, Value, New Issues			299
Shares issued under the DRPlus and 401(k) plan			46
Stock-based compensation activity			11
Capital contribution from parent										0		0			91		91
Net income	$ 1,157													548					609
Net Income (Loss) Available to Common Stockholders, Basic	1,152			1,152						545					$ 607
Common stock dividends				(662)										(9)					(41)
Preferred stock dividends														(3)					(2)
Change in derivative financial instruments					0
Change in deferred retirement benefit costs	(5)					(5)
Net income attributable to noncontrolling interest holders	$ (5)								5
Dividends paid to noncontrolling interest holders									(5)
Stock Issued During Period, Shares, New Issues	3,200,000
Shares issued under the DRPlus and 401(k) plan	600,000
Shares issued (in shares)	500,000
End of year (shares) at Dec. 31, 2023	266,300,000														25,500,000
End of year at Dec. 31, 2023	$ 11,478	3	7,216	4,136	0	(6)	(6)		129		511	2,725	80	3,647		0	3,020	49	3,756
Stockholders' equity, end of year at Dec. 31, 2023	$ 11,349							11,349		6,963					$ 6,825
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.52
Stock Issued During Period, Value, New Issues			233
Shares issued under the DRPlus and 401(k) plan			40
Stock-based compensation activity			24
Capital contribution from parent										476		476			36		36
Net income	$ 1,187													562					622
Net Income (Loss) Available to Common Stockholders, Basic	1,182			1,182						$ 559					$ 620
Common stock dividends				(714)										0					(110)
Preferred stock dividends														(3)					(2)
Change in derivative financial instruments					(3)
Change in deferred retirement benefit costs	(3)					(3)
Net income attributable to noncontrolling interest holders	$ (5)								5
Dividends paid to noncontrolling interest holders									(5)
Stock Issued During Period, Shares, New Issues	2,900,000
Shares issued under the DRPlus and 401(k) plan	500,000
Shares issued (in shares)	200,000
End of year (shares) at Dec. 31, 2024	269,900,000									102,100,000					25,500,000
End of year at Dec. 31, 2024	$ 12,243	$ 3	$ 7,513	$ 4,604	$ 3	$ (9)	$ (6)		$ 129		$ 511	$ 3,201	$ 80	$ 4,206		$ 0	$ 3,056	$ 49	$ 4,266
Stockholders' equity, end of year at Dec. 31, 2024	$ 12,114							$ 12,114		$ 7,998					$ 7,371
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.68