Long-Term Debt And Equity Financings (Schedule Of Maturities Of Long-Term Debt) (Details) $ in Millions	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
2015	$ 395
2016	681
2017	840
2018	581
2019	442
Thereafter	4,392
Total	7,331
Parent Company
Debt Instrument [Line Items]
2019	350	[1]
Thereafter	350	[1]
Total	700	[1]
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	(6)
Union Electric Company
Debt Instrument [Line Items]
2015	266	[1]
2016	431	[1]
2017	383	[1]
2018	581	[1]
2019	92	[1]
Thereafter	2,382	[1]
Total	4,135	[1]
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	25
Ameren Illinois Company
Debt Instrument [Line Items]
2015	129	[1]
2016	250	[1]
2017	457	[1]
Thereafter	1,660	[1]
Total	2,496	[1]
Debt Instrument, Unamortized Discount or Premium and Debt Issuance Costs	$ 25

[1] Excludes unamortized discount and premium and debt issuance costs of $6 million, $25 million, and $25 million at Ameren (parent), Ameren Missouri, and Ameren Illinois, respectively.