Consolidated Statement Of Income (Loss) (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension and other postretirement activity, tax (benefit)	$ 3	$ (7)	$ 16
Ameren Illinois Company
Pension and other postretirement activity, tax (benefit)	$ (2)	$ (2)	$ (2)