Income Taxes Income Taxes (Tables)

3 Months Ended

Mar. 31, 2019

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, 2019 and 2018:

	Ameren			Ameren Missouri			Ameren Illinois
Three Months	2019	2018		2019	2018		2019	2018
Federal statutory corporate income tax rate:	21%	21%		21%	21%		21%	21%
Increases (decreases) from:
Amortization of excess deferred taxes	(7)	(2)	(a)	(12)	—	(a)	(3)	(3)
Other depreciation differences	—	—		—	1		—	—
Amortization of deferred investment tax credit	(1)	(1)		(1)	(1)		—	—
State tax	6	7		4	4		7	7
Stock-based compensation	(7)	(3)		—	—		—	—
Other	—	—		(3)	—		—	—
Effective income tax rate	12%	22%		9%	25%		25%	25%