Short-Term Debt And Liquidity (Schedule Of Maximum Aggregate Amount Available On Credit Agreements) (Details) (USD $)	Nov. 14, 2012 Illinois Credit Agreement 2012	Dec. 31, 2013 Illinois Credit Agreement 2012 Parent Company	Dec. 31, 2013 Illinois Credit Agreement 2012 Ameren Illinois Company	Nov. 14, 2012 Missouri Credit Agreement 2012	Dec. 31, 2013 Missouri Credit Agreement 2012 Parent Company	Dec. 31, 2013 Missouri Credit Agreement 2012 Union Electric Company
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100,000,000.0	$ 300,000,000	$ 800,000,000	$ 1,000,000,000	$ 500,000,000	$ 800,000,000

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant