Consolidated Balance Sheet (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Accounts receivable - trade allowance for doubtful accounts	$ 19	$ 18
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	400,000,000	400,000,000
Common Stock, Shares, Outstanding	245,600,000	244,500,000
Union Electric Company
Accounts receivable - trade allowance for doubtful accounts	$ 7	$ 7
Common stock, par value (in dollars per share)	$ 5	$ 5
Common stock, shares authorized (in shares)	150,000,000	150,000,000
Common Stock, Shares, Outstanding	102,100,000	102,100,000
Ameren Illinois Company
Accounts receivable - trade allowance for doubtful accounts	$ 12	$ 11
Common stock, no par value (in dollars per share)	$ 0	$ 0
Common stock, shares authorized (in shares)	45,000,000	45,000,000
Common Stock, Shares, Outstanding	25,500,000	25,500,000