Schedule I - Condensed Financial Information Of Parent (Statement of Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Condensed Financial Statements, Captions [Line Items]
Operating revenues	$ 7,623	$ 7,500	$ 7,957
Operating expenses	6,107	5,942	6,442
Operating loss	1,516	1,558	1,515
Equity in earnings of subsidiaries	(4)	1	2
Interest income from affiliates	41	32	11
Total other income (expense), net	417	348	226
Interest Charges	(663)	(566)	(486)
Income tax benefit	83	183	176
Comprehensive Income from Continuing Operations
Pension and other postretirement benefit plan activity, net of income taxes (benefit) of $—, $(2), and $(4), respectively	(3)	(5)	(14)
Unrealized net gain on derivative hedging instruments, net of income taxes of $—, $—, and $—, respectively	3	0	0
Comprehensive Income Attributable to Ameren Common Shareholders	1,182	1,147	1,060
Other Comprehensive Income (Loss), Taxes:
Pension and other postretirement benefit plan activity, tax (benefit)	0	(2)	(4)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	0	0	0
Ameren (parent)
Condensed Financial Statements, Captions [Line Items]
Operating revenues	0	0	0
Operating expenses	17	22	15
Operating loss	(17)	(22)	(15)
Equity in earnings of subsidiaries	1,271	1,245	1,161
Interest income from affiliates	14	10	2
Total other income (expense), net	3	(11)	(13)
Interest Charges	(162)	(119)	(86)
Income tax benefit	61	49	25
Net Income Attributable to Ameren Common Shareholders	1,170	1,152	1,074
Comprehensive Income from Continuing Operations
Pension and other postretirement benefit plan activity, net of income taxes (benefit) of $—, $(2), and $(4), respectively	(3)	(5)	(14)
Unrealized net gain on derivative hedging instruments, net of income taxes of $—, $—, and $—, respectively	(3)	0	0
Comprehensive Income Attributable to Ameren Common Shareholders	1,170	1,147	1,060
Other Comprehensive Income (Loss), Taxes:
Pension and other postretirement benefit plan activity, tax (benefit)	$ 0	$ (2)	$ (4)