Consolidated Statement Of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest Paid, Capitalized, Investing Activities	$ 20	$ 21	$ 14
Union Electric Company
Interest Paid, Capitalized, Investing Activities	12	14	10
Ameren Illinois Company
Interest Paid, Capitalized, Investing Activities	$ 8	$ 7	$ 4