Income Taxes Income Taxes (Tables)

3 Months Ended

Mar. 31, 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 months ended March 31, 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)	(1)	—	—
Amortization of excess deferred taxes	(9)	(9)	(17)	(15)	(2)	(3)
Depreciation differences	—	(1)	1	—	(1)	(1)
Renewable and other tax credits	(6)	—	(11)	—	—	—
State tax	6	6	3	3	7	7
Stock-based compensation	(1)	(5)	—	—	—	—
Effective income tax rate	10%	12%	(4)%	8%	25%	24%