Consolidated Statement of Income (Loss) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension and other postretirement benefit plan activity, tax expense (benefit)	$ 3	$ 8	$ 3	$ 8
Ameren Illinois Company
Pension and other postretirement benefit plan activity, tax expense (benefit)			$ (1)	$ (1)