Long-Term Debt And Equity Financings (Schedule Of Long-Term Debt Outstanding) (Details) (USD $)					12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended					12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended					12 Months Ended						12 Months Ended					12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended						12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended					12 Months Ended					12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended					12 Months Ended				12 Months Ended				12 Months Ended						12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Parent Company	Dec. 31, 2012 Parent Company	Dec. 31, 2013 Parent Company 8.875% Senior unsecured notes due 2014	Dec. 31, 2012 Parent Company 8.875% Senior unsecured notes due 2014	Dec. 31, 2013 Union Electric Company	Dec. 31, 2012 Union Electric Company	Dec. 31, 2013 Union Electric Company City Of Bowling Green Capital Lease Peno Creek Ct	Dec. 31, 2012 Union Electric Company City Of Bowling Green Capital Lease Peno Creek Ct	Dec. 31, 2013 Union Electric Company Audrain County Capital Lease Audrain County Ct	Dec. 31, 2012 Union Electric Company Audrain County Capital Lease Audrain County Ct	Dec. 31, 2013 Ameren Illinois Company	Dec. 31, 2012 Ameren Illinois Company	Jan. 31, 2014 Ameren Illinois Company		Sep. 20, 2012 Secured Debt Union Electric Company 5.25% Senior secured notes due 2012	Dec. 31, 2013 Secured Debt Union Electric Company 4.65% Senior secured notes due 2013		Oct. 31, 2013 Secured Debt Union Electric Company 4.65% Senior secured notes due 2013	Dec. 31, 2012 Secured Debt Union Electric Company 4.65% Senior secured notes due 2013		Dec. 31, 2013 Secured Debt Union Electric Company 5.50% Senior secured notes due 2014		Dec. 31, 2012 Secured Debt Union Electric Company 5.50% Senior secured notes due 2014		Dec. 31, 2013 Secured Debt Union Electric Company 4.75% Senior secured notes due 2015		Dec. 31, 2012 Secured Debt Union Electric Company 4.75% Senior secured notes due 2015		Dec. 31, 2013 Secured Debt Union Electric Company 5.40% Senior secured notes due 2016		Dec. 31, 2012 Secured Debt Union Electric Company 5.40% Senior secured notes due 2016		Dec. 31, 2013 Secured Debt Union Electric Company 6.40% Senior secured notes due 2017		Dec. 31, 2012 Secured Debt Union Electric Company 6.40% Senior secured notes due 2017		Dec. 31, 2013 Secured Debt Union Electric Company 6.00% Senior secured notes due 2018		Dec. 31, 2012 Secured Debt Union Electric Company 6.00% Senior secured notes due 2018		Sep. 20, 2012 Secured Debt Union Electric Company 6.00% Senior secured notes due 2018	Dec. 31, 2013 Secured Debt Union Electric Company 5.10% Senior secured notes due 2018		Dec. 31, 2012 Secured Debt Union Electric Company 5.10% Senior secured notes due 2018		Sep. 20, 2012 Secured Debt Union Electric Company 5.10% Senior secured notes due 2018		Dec. 31, 2013 Secured Debt Union Electric Company 6.70% Senior secured notes due 2019		Dec. 31, 2012 Secured Debt Union Electric Company 6.70% Senior secured notes due 2019		Sep. 20, 2012 Secured Debt Union Electric Company 6.70% Senior secured notes due 2019	Dec. 31, 2013 Secured Debt Union Electric Company 5.10% Senior secured notes due 2019		Dec. 31, 2012 Secured Debt Union Electric Company 5.10% Senior secured notes due 2019		Sep. 20, 2012 Secured Debt Union Electric Company 5.10% Senior secured notes due 2019	Dec. 31, 2013 Secured Debt Union Electric Company 5.00% Senior secured notes due 2020		Dec. 31, 2012 Secured Debt Union Electric Company 5.00% Senior secured notes due 2020		Dec. 31, 2013 Secured Debt Union Electric Company 5.50% Senior secured notes due 2034		Dec. 31, 2012 Secured Debt Union Electric Company 5.50% Senior secured notes due 2034		Dec. 31, 2013 Secured Debt Union Electric Company 5.30% Senior secured notes due 2037		Dec. 31, 2012 Secured Debt Union Electric Company 5.30% Senior secured notes due 2037		Dec. 31, 2013 Secured Debt Union Electric Company 8.45% Senior secured notes due 2039		Dec. 31, 2012 Secured Debt Union Electric Company 8.45% Senior secured notes due 2039		Dec. 31, 2013 Secured Debt Union Electric Company 3.90% Senior secured notes due 2042		Dec. 31, 2012 Secured Debt Union Electric Company 3.90% Senior secured notes due 2042		Sep. 20, 2012 Secured Debt Union Electric Company 3.90% Senior secured notes due 2042	Sep. 11, 2012 Secured Debt Union Electric Company 3.90% Senior secured notes due 2042	Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 8.875% Due 2013		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 8.875% Due 2013		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.20% Due 2016		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.20% Due 2016		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.25% Due 2016		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.25% Due 2016		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.125% Due 2017		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.125% Due 2017		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.25% Due 2018		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.25% Due 2018		Aug. 27, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.25% Due 2018	Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 9.75% Due 2018		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 9.75% Due 2018		Aug. 27, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 9.75% Due 2018	Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes, 2.70%, Due 2022		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes, 2.70%, Due 2022		Aug. 20, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes, 2.70%, Due 2022	Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.125% Due 2028		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.125% Due 2028		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.70% Due 2036		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.70% Due 2036		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 6.70% Due 2036		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 6.70% Due 2036		Dec. 31, 2013 Secured Debt Ameren Illinois Company Senior Secured Notes 4.80% Due 2043		Dec. 31, 2012 Secured Debt Ameren Illinois Company Senior Secured Notes 4.80% Due 2043		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1992 Series due 2022		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1992 Series due 2022		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1993 5.45% Series due 2028		Oct. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1993 5.45% Series due 2028	Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1993 5.45% Series due 2028		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series A due 2033		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series A due 2033		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series B due 2033		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series B due 2033		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series C due 2033		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Union Electric Company 1998 Series C due 2033		Nov. 30, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series1992 B 6.20% Due 2012	Aug. 27, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series A 2000 5.50% Due 2014	Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series 1993 5.90% Due 2023		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series 1993 5.90% Due 2023		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series 1994 A 5.70% Due 2024		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series 1994 A 5.70% Due 2024		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series C-1 1993 5.95% Due 2026		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series C-1 1993 5.95% Due 2026		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series C-2 1993 5.70% Due 2026		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series C-2 1993 5.70% Due 2026		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series B-1 1993 Due 2028		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series B-1 1993 Due 2028		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series1998A 5.40% Due 2028		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series1998A 5.40% Due 2028		Dec. 31, 2013 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series1998B 5.40% Due 2028		Dec. 31, 2012 Environmental Improvement And Pollution Control Revenue Bonds Ameren Illinois Company Series1998B 5.40% Due 2028
Debt Instrument [Line Items]
Debt instrument face amount					$ 425,000,000	$ 425,000,000									$ 1,000,000	[1]			[2]		$ 200,000,000	[2]	$ 104,000,000	[2]	$ 104,000,000	[2]	$ 114,000,000	[2]	$ 114,000,000	[2]	$ 260,000,000	[2]	$ 260,000,000	[2]	$ 425,000,000	[2]	$ 425,000,000	[2]	$ 179,000,000	[2],[3]	$ 179,000,000	[2],[3]	$ 179,000,000	$ 199,000,000	[2]	$ 199,000,000	[2]	$ 199,000,000	[4]	$ 329,000,000	[2],[3]	$ 329,000,000	[2],[3]	$ 329,000,000	$ 244,000,000	[2]	$ 244,000,000	[2]	$ 244,000,000	$ 85,000,000	[2]	$ 85,000,000	[2]	$ 184,000,000	[2]	$ 184,000,000	[2]	$ 300,000,000	[2]	$ 300,000,000	[2]	$ 350,000,000	[2],[3]	$ 350,000,000	[2],[3]	$ 485,000,000	[2],[3]	$ 485,000,000	[2],[3]	$ 485,000,000	$ 485,000,000		[5]	$ 150,000,000	[5]	$ 54,000,000	[5]	$ 54,000,000	[5]	$ 75,000,000	[6]	$ 75,000,000	[6]	$ 250,000,000	[6],[7]	$ 250,000,000	[6],[7]	$ 144,000,000	[6],[7]	$ 144,000,000	[6],[7]	$ 144,000,000	$ 313,000,000	[6],[7]	$ 313,000,000	[6],[7]	$ 313,000,000	$ 400,000,000	[6],[7]	$ 400,000,000	[6],[7]	$ 400,000,000	$ 60,000,000	[6]	$ 60,000,000	[6]	$ 61,000,000	[6]	$ 61,000,000	[6]	$ 42,000,000	[5]	$ 42,000,000	[5]	$ 280,000,000	[6]	$ 0	[6]	$ 47,000,000	[8],[9]	$ 47,000,000	[8],[9]	$ 1,000,000	[10]		$ 44,000,000	[10]	$ 60,000,000	[8],[9]	$ 60,000,000	[8],[9]	$ 50,000,000	[8],[9]	$ 50,000,000	[8],[9]	$ 50,000,000	[8],[9]	$ 50,000,000	[8],[9]			$ 32,000,000	[11]	$ 32,000,000	[11]	$ 36,000,000	[1]	$ 36,000,000	[1]	$ 35,000,000	[12]	$ 35,000,000	[12]	$ 8,000,000	[12]	$ 8,000,000	[12]	$ 17,000,000	[12],[8]	$ 17,000,000	[12],[8]	$ 19,000,000	[1]	$ 19,000,000	[1]	$ 33,000,000	[1]	$ 33,000,000	[1]
Capital lease obligations									59,000,000	64,000,000	240,000,000	240,000,000
Fair-market value adjustments													4,000,000	4,000,000
Long-term debt, gross							3,764,000,000	4,013,000,000					1,863,000,000	1,733,000,000
Less: Unamortized discount and premium				1,000,000			7,000,000	7,000,000					7,000,000	6,000,000
Less: Maturities due within one year	(534,000,000)	(355,000,000)	(425,000,000)				(109,000,000)	(205,000,000)						(150,000,000)
Long-term Debt, Net	$ 5,504,000,000	$ 5,802,000,000		$ 424,000,000			$ 3,648,000,000	$ 3,801,000,000					$ 1,856,000,000	$ 1,577,000,000
Long-term debt interest rate					8.875%												5.25%	4.65%		4.65%			5.50%				4.75%				5.40%				6.40%				6.00%				6.00%	5.10%				5.10%		6.70%				6.70%	5.10%				5.10%	5.00%				5.50%				5.30%				8.45%				3.90%				3.90%	3.90%	8.875%				6.20%				6.25%				6.125%				6.25%				6.25%	9.75%				9.75%	2.70%				2.70%	6.125%				6.70%				6.70%				4.80%								5.45%		5.45%															6.20%	5.50%	5.90%				5.70%				5.95%				5.70%								5.40%				5.40%
Long-term debt maturity date					2014				2022		2033							2013					2014				2015				2016				2017				2018					2018						2019					2019					2020				2034				2037				2039				2042						2013				2016				2016				2017				2018					2018					2022					2028				2036				2036				2043				2022				2028					2033				2033				2033						2023				2024				2026				2026				2028				2028				2028
Debt instrument, interest rate, maximum																																																																																																																																	18.00%									18.00%				18.00%				18.00%
Redemption price, percentage																																																																																																																																					100.00%																			100.00%				100.00%				100.00%				100.00%				100.00%				100.00%				100.00%

[1] These bonds are mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture and are secured by substantially all property of the former IP and CIPS. The bonds are callable at 100% of par value. The bonds are also backed by an insurance guarantee policy.

[2] These notes are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any first mortgage bonds issued under the Ameren Missouri mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Missouri first mortgage bonds and senior secured notes currently outstanding, and assuming no early retirement of any series of such securities in full, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2042.

[3] Ameren Missouri has agreed, during the life of these notes, not to optionally redeem, purchase or otherwise retire in full its first mortgage bonds. Ameren Missouri has also agreed to prevent a first mortgage bond release date from occurring as long as any of the 8.45% senior secured notes due 2039 and any of the 3.90% senior secured notes due 2042 remain outstanding.

[4] Amount is less than $1 million.

[5] These notes are collaterally secured by first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the CILCO mortgage indenture remain outstanding. Redemption, purchase, or maturity of all first mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the first mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the CILCO first mortgage bonds and senior secured notes currently outstanding, and assuming no early retirement of any series of such securities in full, we do not expect the first mortgage bond lien protection associated with these notes to fall away until 2023.

[6] These notes are collaterally secured by mortgage bonds issued by Ameren Illinois under the Ameren Illinois mortgage indenture. The notes have a fall-away lien provision and will remain secured only as long as any series of first mortgage bonds issued under the Ameren Illinois mortgage indenture remain outstanding. Redemption, purchase, or maturity of all mortgage bonds, including first mortgage bonds currently outstanding and any that may be issued in the future, would result in a release of the mortgage bonds currently securing these notes, at which time these notes would become unsecured obligations. Considering the Ameren Illinois mortgage bonds and senior secured notes currently outstanding, and assuming no early retirement of any series of such securities in full, we do not expect the mortgage bond lien protection associated with these notes to fall away until 2028.

[7] Ameren Illinois has agreed, during the life of these notes, not to optionally redeem, purchase, or otherwise retire in full its Ameren Illinois mortgage bonds; therefore, an Ameren Illinois first mortgage bond release date will not occur as long as any of these notes are outstanding.

[8] Interest rates, and periods during which such rates apply, vary depending on our selection of defined rate modes. Maximum interest rates could range up to 18% depending on the series of bonds. The average interest rates for 2013 and 2012 were as follows: 2013 2012Ameren Missouri 1992 Series0.17% 0.30%Ameren Missouri 1998 Series A0.34% 0.65%Ameren Missouri 1998 Series B0.33% 0.64%Ameren Missouri 1998 Series C0.34% 0.64%Ameren Illinois 1993 Series B-10.14% 0.22%

[9] These bonds are collaterally secured by first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage indenture and have a fall-away lien provision similar to that of Ameren Missouri's senior secured notes. The bonds are also backed by an insurance guarantee policy.

[10] These bonds are first mortgage bonds issued by Ameren Missouri under the Ameren Missouri mortgage bond indenture and are secured by substantially all Ameren Missouri property and franchises. The bonds are callable at 100% of par value. Less than $1 million principal amount of the bonds remain outstanding.

[11] These bonds are first mortgage bonds issued by Ameren Illinois under the CILCO mortgage indenture and are secured by substantially all property of the former CILCO. The bonds are callable at 100% of par value.

[12] The bonds are callable at 100% of par value.