Consolidated Statement of Comprehensive Income (Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Income from Continuing Operations	$ 110	$ 99
Other Comprehensive Income from Continuing Operations, Net Of Taxes	0	0
Other Comprehensive Income from Continuing Operations, Net of Taxes
Comprehensive Income from Continuing Operations	110	99
Less: Comprehensive Income from Continuing Operations Attributable to Noncontrolling Interests	2	2
Comprehensive Income from Continuing Operations Attributable to Ameren Corporation	108	97
Loss from Discontinued Operations, Net of Taxes	0	(1)
Other Comprehensive Loss from Discontinued Operations, Net of Taxes	0	0
Comprehensive Loss from Discontinued Operations Attributable to Ameren Corporation	0	(1)
Comprehensive Income	$ 108us-gaap_ComprehensiveIncomeNetOfTax	$ 96us-gaap_ComprehensiveIncomeNetOfTax

Comprehensive Income (Loss) from Continuing Operations, Net of Tax, Attributable to Noncontrolling Interest

No definition available.

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- Definition

Comprehensive Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest

+ References

No definition available.

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- Definition

Comprehensive Income (Loss) from Continuing Operations, Net of Tax, Portion Attributable to Parent

+ References

No definition available.

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Comprehensive Income (Loss) from Discontinued Operations, Net of Tax, Portion Attributable to Parent

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- Definition

Other Comprehensive Income (Loss) From Continuing Operations, Net Of Tax, Including Portion Attributable To Noncontrolling Interest

+ References

No definition available.

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Other Comprehensive Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest

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No definition available.

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- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before extraordinary items, and noncontrolling interest.

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- Definition

Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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