Consolidated Statement Of Income (Parenthetical) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension and other postretirement activity, tax (benefit)	$ 16	$ (6)	$ (14)
Ameren Illinois Company
Pension and other postretirement activity, tax (benefit)	$ 2	$ 2	$ 2