XML 148 R115.htm IDEA: XBRL DOCUMENT

Income Taxes (Reconciliation Of The Change In The Liability For Interest On Unrecognized Tax Benefits) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Contingency [Line Items]
Liability for interest	$ 5	$ 17	$ 8
Interest charges (income)	1	(11)	9
Interest payment		(1)
Liability for interest	6	5	17
Union Electric Company [Member]
Income Tax Contingency [Line Items]
Liability for interest	6	10	4
Interest charges (income)	2	(3)	6
Interest payment		(1)
Liability for interest	8	6	10
Ameren Illinois Company [Member]
Income Tax Contingency [Line Items]
Liability for interest	1	2
Interest charges (income)		(1)	2
Interest payment
Liability for interest	$ 1	$ 1	$ 2

This element represents the amount of interest expense accrued as of the date of the statement of financial position for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

+ References+ Details

- Definition

This element represents interest expense recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity.

+ References+ Details