Schedule I - Condensed Financial Information Of Parent (Statement of Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Condensed Financial Statements, Captions [Line Items]
Operating revenues	$ 7,957	$ 6,394	$ 5,794
Operating expenses	6,442	5,061	4,494
Operating loss	1,515	1,333	1,300
Equity in earnings of subsidiaries	2	12	3
Interest income from affiliates	11	2	4
Total other expense, net	226	202	151
Interest Charges	(486)	(383)	(419)
Income tax benefit	176	157	155
Comprehensive Income from Continuing Operations
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(14)	14	16
Comprehensive Income Attributable to Ameren Common Shareholders	1,060	1,004	887
Other Comprehensive Income (Loss), Taxes:
Pension and other postretirement benefit plan activity, tax (benefit)	(4)	4	5
Parent Company
Condensed Financial Statements, Captions [Line Items]
Operating revenues	0	0	0
Operating expenses	15	13	12
Operating loss	(15)	(13)	(12)
Equity in earnings of subsidiaries	1,161	1,039	908
Interest income from affiliates	2	3	4
Total other expense, net	(13)	0	(8)
Interest Charges	(86)	(64)	(57)
Income tax benefit	25	25	36
Net Income Attributable to Ameren Common Shareholders	1,074	990	871
Comprehensive Income from Continuing Operations
Pension and other postretirement benefit plan activity, net of income taxes (benefit)	(14)	14	16
Comprehensive Income Attributable to Ameren Common Shareholders	1,060	1,004	887
Other Comprehensive Income (Loss), Taxes:
Pension and other postretirement benefit plan activity, tax (benefit)	$ (4)	$ 4	$ 5