Consolidated Statement Of Cash Flows (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Interest Paid, Capitalized	$ 15	$ 17	$ 18
Union Electric Company
Interest Paid, Capitalized	12	12	16
Ameren Illinois Company
Interest Paid, Capitalized	$ 3	$ 5	$ 2