Consolidated Statement Of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest Paid, Capitalized, Investing Activities	$ 21	$ 14	$ 15
Union Electric Company
Interest Paid, Capitalized, Investing Activities	14	10	12
Ameren Illinois Company
Interest Paid, Capitalized, Investing Activities	$ 7	$ 4	$ 3