Schedule I - Condensed Financial Information Of Parent (Statement of Cash Flows) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Condensed Financial Statements, Captions [Line Items]
Net cash flows provided by operating activities	$ 2,564	$ 2,263	$ 1,661
Cash Flows From Investing Activities:
Other	(1)	23	8
Net cash flows provided by (used in) investing activities	(3,798)	(3,370)	(3,528)
Cash flows from financing activities:
Dividends on common stock	(662)	(610)	(565)
Short-term debt, net	(533)	522	55
Maturities of long-term debt	(100)	(505)	(8)
Issuances of long-term debt	2,295	1,467	1,997
Issuances of common stock	346	333	308
Employee payroll taxes related to stock-based compensation	(20)	(16)	(17)
Debt issuance costs	(21)	(18)	(18)
Net cash flows provided by (used in) financing activities	1,290	1,168	1,721
Cash, cash equivalents, and restricted cash at beginning of year	216	155	301
Cash, cash equivalents, and restricted cash at end of year	272	216	155
Noncash Investing and Financing Items [Abstract]
Stock Issued		31
Ameren (parent)
Condensed Financial Statements, Captions [Line Items]
Net cash flows provided by operating activities	171	44	79
Cash Flows From Investing Activities:
Money pool advances, net		40
Money pool advances, net	(530)		(92)
Notes receivable – ATXI	0	35	40
Investments in subsidiaries	(109)	(30)	(489)
Other	5	3	7
Net cash flows provided by (used in) investing activities	(634)	48	(534)
Cash flows from financing activities:
Dividends on common stock	(662)	(610)	(565)
Short-term debt, net	(475)	198	(213)
Issuances of long-term debt	1,298	0	949
Issuances of common stock	346	333	308
Employee payroll taxes related to stock-based compensation	(20)	(16)	(17)
Debt issuance costs	(8)	(1)	(7)
Net cash flows provided by (used in) financing activities	479	(96)	455
Net change in cash, cash equivalents, and restricted cash	16	(4)	0
Cash, cash equivalents, and restricted cash at beginning of year	0	4	4
Cash, cash equivalents, and restricted cash at end of year	16	0	4
Cash dividends received from consolidated subsidiaries	173	76	123
Noncash Investing and Financing Items [Abstract]
Stock Issued	$ 40	$ 31	$ 33