Income Taxes Income Taxes (Tables)

6 Months Ended

Jun. 30, 2021

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation

The following table presents a reconciliation of the federal statutory corporate income tax rate to the effective income tax rate for the three and six months ended June 30, 2021 and 2020:

	Ameren					Ameren Missouri					Ameren Illinois
	2021			2020		2021			2020		2021		2020
Three Months
Federal statutory corporate income tax rate	21	%		21	%	21	%		21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—			—		(1)			(1)		—		—
Amortization of excess deferred taxes	(9)			(9)		(17)			(16)		(2)		(3)
Depreciation differences	—			—		1			—		1		1
Renewable and other tax credits	(4)		(a)	—		(10)		(a)	—		(1)		—
State tax	5			5		3			3		7		7
Effective income tax rate	13	%		17	%	(3)	%		7	%	26	%	26	%
Six Months
Federal statutory corporate income tax rate	21	%		21	%	21	%		21	%	21	%	21	%
Increases (decreases) from:
Amortization of deferred investment tax credit	—			—		(1)			(1)		—		—
Amortization of excess deferred taxes	(9)			(9)		(17)			(16)		(3)		(3)
Depreciation differences	—			—		1			—		—		—
Renewable and other tax credits	(5)		(a)	—		(10)		(a)	—		—		—
State tax	5			5		3			3		7		7
Stock-based compensation	—			(2)		—			—		—		—

	Ameren				Ameren Missouri				Ameren Illinois
	2021		2020		2021		2020		2021		2020
Effective income tax rate	12	%	15	%	(3)	%	7	%	25	%	25	%

(a)Includes production tax credits associated with the High Prairie and Atchison renewable energy centers. Ameren Missouri placed the High Prairie renewable energy center in service as of December 2020. Additionally, Ameren Missouri placed in service the wind turbines at its Atchison renewable energy center throughout the first half of 2021. The benefit of the production tax credits associated with Missouri renewable energy standard compliance is refunded to customers through the RESRAM.