Consolidated Statement Of Stockholders' Equity - USD ($) $ in Millions	Total	Common Stock	Other Paid-In Capital	Retained Earnings	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, 2020			$ 6,179	$ 2,757	$ (1)			$ 142			$ 2,518		$ 2,101			$ 2,652	$ 62	$ 2,252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of non-ATM program forward sale agreement through common shares issuance			113
Stock Issued During Period, Value, New Issues			148
Shares issued under the DRPlus and 401(k) plan			47
Stock-based compensation activity			15
Capital contribution from parent									$ 207		207			$ 262		262
Net income	$ 995								521				521	427				427
Net Income (Loss) Available to Common Stockholders, Basic	990			990
Common stock dividends				(565)									(24)					0
Preferred stock dividends													(3)					(2)
Change in deferred retirement benefit costs	14				14
Net income attributable to noncontrolling interest holders	$ (5)							5
Dividends paid to noncontrolling interest holders								(5)
Redemptions of preferred stock								(13)									(13)
Beginning of year (shares) at Dec. 31, 2020	253,300,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under non-ATM program forward sale agreement	1,600,000
Stock Issued During Period, Shares, New Issues	1,800,000
Shares issued under the DRPlus and 401(k) plan	500,000
Shares issued (in shares)	500,000
End of year (shares) at Dec. 31, 2021	257,700,000
End of year at Dec. 31, 2021	$ 9,829	$ 3	6,502	3,182	13	$ 13		129		$ 511	2,725	$ 80	2,595		$ 0	2,914	49	2,677
Stockholders' equity, end of year at Dec. 31, 2021							$ 9,700		5,911					5,640
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.20
Settlement of non-ATM program forward sale agreement through common shares issuance			0
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				565	$ 515				515
Net Income (Loss) Available to Common Stockholders, Basic	1,074			1,074
Common stock dividends				(610)									(46)					0
Preferred stock dividends													(3)					(2)
Change in deferred retirement benefit costs	(14)				(14)
Net income attributable to noncontrolling interest holders	$ (5)							5
Dividends paid to noncontrolling interest holders								(5)
Redemptions of preferred stock								0									0
Shares issued under non-ATM program forward sale agreement	0
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								102,100,000					25,500,000
End of year at Dec. 31, 2022	$ 10,637	3	6,860	3,646	(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						10,508		$ 6,427					$ 6,168
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.36
Settlement of non-ATM program forward sale agreement through common shares issuance			0
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				548	$ 609				609
Net Income (Loss) Available to Common Stockholders, Basic	1,152			1,152
Common stock dividends				(662)									(9)					(41)
Preferred stock dividends													(3)					(2)
Change in deferred retirement benefit costs	(5)				(5)
Net income attributable to noncontrolling interest holders	$ (5)							5
Dividends paid to noncontrolling interest holders								(5)
Redemptions of preferred stock								0									0
Shares issued under non-ATM program forward sale agreement	0
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								102,100,000					25,500,000
End of year at Dec. 31, 2023	$ 11,478	$ 3	$ 7,216	$ 4,136	$ (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