Consolidated Statement of Income (Loss) (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension and other postretirement benefit plan activity, tax expense (benefit)	$ 0	$ 0	$ 4	$ 3
Ameren Illinois Company
Pension and other postretirement benefit plan activity, tax expense (benefit)	$ (1)	$ (1)	$ (2)	$ (2)