Schedule I - Condensed Financial Information Of Parent (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	$ 2,763	$ 2,564	$ 2,263
Cash Flows From Investing Activities:
Other	(26)	(1)	23
Net cash provided by (used in) investing activities	(4,456)	(3,798)	(3,370)
Cash flows from financing activities:
Dividends on common stock	(714)	(662)	(610)
Short-term debt, net	607	(533)	522
Maturities and extinguishment of long-term debt	(893)	(100)	(505)
Issuances of long-term debt	2,535	2,295	1,467
Issuances of common stock	273	346	333
Employee payroll taxes related to stock-based compensation	(8)	(20)	(16)
Debt issuance costs	(31)	(21)	(18)
Net cash provided by (used in) financing activities	1,749	1,290	1,168
Cash, cash equivalents, and restricted cash at beginning of year	272	216	155
Cash, cash equivalents, and restricted cash at end of year	328	272	216
Noncash Investing and Financing Items [Abstract]
Stock Issued		40
Ameren (parent)
Condensed Financial Statements, Captions [Line Items]
Net cash provided by (used in) operating activities	(65)	171	44
Cash Flows From Investing Activities:
Money pool advances, net	495		40
Money pool advances, net		(530)
Notes receivable – ATXI	0	0	35
Investments in subsidiaries	(557)	(109)	(30)
Investments in subsidiary debt securities	44	0	0
Other	1	5	3
Net cash provided by (used in) investing activities	(105)	(634)	48
Cash flows from financing activities:
Dividends on common stock	(714)	(662)	(610)
Short-term debt, net	1,054	(475)	198
Maturities and extinguishment of long-term debt	(450)	0	0
Issuances of long-term debt	0	1,298	0
Issuances of common stock	273	346	333
Employee payroll taxes related to stock-based compensation	(8)	(20)	(16)
Debt issuance costs	(1)	(8)	(1)
Net cash provided by (used in) financing activities	154	479	(96)
Net change in cash, cash equivalents, and restricted cash	(16)	16	(4)
Cash, cash equivalents, and restricted cash at beginning of year	16	0	4
Cash, cash equivalents, and restricted cash at end of year	0	16	0
Cash dividends received from consolidated subsidiaries	140	173	76
Noncash Investing and Financing Items [Abstract]
Stock Issued	$ 16	$ 40	$ 31