Consolidated Statement Of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest Paid, Capitalized, Investing Activities	$ 16	$ 20	$ 21
Union Electric Company
Interest Paid, Capitalized, Investing Activities	10	12	14
Ameren Illinois Company
Interest Paid, Capitalized, Investing Activities	$ 6	$ 8	$ 7