Consolidated Statement Of Income (Parenthetical) (Ameren Illinois Company [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Ameren Illinois Company [Member]
Pension and other postretirement benefit plan activity, tax benefit	$ (2)	$ (2)	$ (2)

Tax effect, net of reclassification adjustments, of the change in accumulated other comprehensive income (loss) related to pension and other postretirement benefit plans, attributable to the parent entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569643-111683

+ Details