Retirement Benefits (Tables)

3 Months Ended

Mar. 31, 2021

Retirement Benefits [Abstract]

Components Of Net Periodic Benefit Cost

The following table presents the components of the net periodic benefit cost (income) incurred for Ameren’s pension and postretirement benefit plans for the three months ended March 31, 2021 and 2020:

	Pension Benefits				Postretirement Benefits
	Three Months				Three Months
	2021		2020		2021		2020
Service cost(a)	$	33	$	27	$	6	$	4
Non-service cost components:
Interest cost	38		43		8		10
Expected return on plan assets	(75)		(73)		(20)		(20)
Amortization of:
Prior service benefit	—		—		(1)		(1)
Actuarial loss (gain)	17		14		(1)		(2)
Total non-service cost components(b)	$	(20)	$	(16)	$	(14)	$	(13)
Net periodic benefit cost (income)	$	13	$	11	$	(8)	$	(9)

(a)Service cost, net of capitalization, is reflected in “Operating Expenses – Other operations and maintenance” on Ameren’s statement of income.

(b)Non-service cost components are reflected in “Other Income, Net” on Ameren’s statement of income. See Note 5 – Other Income, Net, for additional information.

Summary Of Benefit Plan Costs Incurred

Ameren Missouri and Ameren Illinois are responsible for their respective share of Ameren’s pension and other postretirement costs. The following table presents the respective share of net periodic pension and other postretirement benefit costs (income) incurred for the three months ended March 31, 2021 and 2020:

	Pension Benefits				Postretirement Benefits
	Three Months				Three Months
	2021		2020		2021		2020
Ameren Missouri(a)	$	6	$	4	$	(1)	$	(1)
Ameren Illinois	8		7		(7)		(8)
Other	(1)		—		—		—
Ameren(a)	$	13	$	11	$	(8)	$	(9)

(a)Does not include the impact of the regulatory tracking mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri under GAAP and the level of such costs included in rates.