Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Accounts Receivable, Allowance for Credit Loss, Current	$ 41	$ 30
Regulatory Asset	2,569	2,397
Current maturities of long-term debt	17	317
Long-term debt, net	$ 18,354	$ 17,262
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000.0	400,000,000.0
Common Stock, Shares, Outstanding	270,300,000	269,900,000
Variable Interest Entity, Primary Beneficiary
Regulatory Asset	$ 459	$ 465
Current maturities of long-term debt	17	17
Long-term debt, net	449	448
Union Electric Company
Accounts Receivable, Allowance for Credit Loss, Current	12	12
Regulatory Asset	1,401	1,366
Current maturities of long-term debt	$ 17	$ 17
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000.0	150,000,000.0
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Union Electric Company | Variable Interest Entity, Primary Beneficiary
Regulatory Asset	$ 459	$ 465
Current maturities of long-term debt	17	17
Long-term debt, net	449	448
Ameren Illinois Company
Accounts Receivable, Allowance for Credit Loss, Current	29	18
Regulatory Asset	1,143	1,011
Current maturities of long-term debt	$ 0	$ 300
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000.0	45,000,000.0
Common Stock, Shares, Outstanding	25,500,000	25,500,000