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	Union Electric Company	Union Electric Company Common Stock	Union Electric Company Other Paid-In Capital	Union Electric Company Preferred Stock Not Subject To Mandatory Redemption	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 Not Subject To Mandatory Redemption	Ameren Illinois Company Retained Earnings
Beginning of year at Dec. 31, 2019		$ 2	$ 5,694	$ 2,380	$ (17)			$ 142			$ 2,027		$ 1,731			$ 2,188	$ 62	$ 1,882
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Settlement of forward sale agreement through common shares issuance		1	424
Stock Issued During Period, Value, New Issues			0
Shares issued under the DRPlus and 401(k) plan			51
Stock-based compensation activity			10
Capital contribution from parent									$ 491		491			$ 464		464
Net income	$ 877								439				439	382				382
Net Income (Loss) Available to Common Stockholders, Basic	871			871
Common stock dividends				(494)									(66)					(9)
Preferred stock dividends													(3)					(3)
Change in deferred retirement benefit costs	16				16
Net income attributable to noncontrolling interest holders	$ (6)							6
Dividends paid to noncontrolling interest holders								(6)
Redemptions of preferred stock								0									0
Beginning of year (shares) at Dec. 31, 2019	246,200,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares issued under forward sale agreement	5,900,000
Stock Issued During Period, Shares, New Issues	0
Shares issued under the DRPlus and 401(k) plan	700,000
Stock Issued During Period, Shares, Other	500,000
End of year (shares) at Dec. 31, 2020	253,300,000
End of year at Dec. 31, 2020	$ 9,080	3	6,179	2,757	(1)	$ (1)		142		$ 511	2,518	$ 80	2,101		$ 0	2,652	62	2,252
Stockholders' equity, end of year at Dec. 31, 2020							$ 8,938		5,210					4,966
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.00
Settlement of forward sale agreement through common shares issuance		0	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)
Shares issued under 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
Stock Issued During Period, Shares, Other	500,000
End of year (shares) at Dec. 31, 2021	257,700,000								102,100,000					25,500,000
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						9,700		$ 5,911					$ 5,640
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Cash Paid	$ 2.20
Settlement of forward sale agreement through common shares issuance		0	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 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
Stock Issued During Period, Shares, Other	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