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Retirement Benefits (Tables)
 12 Months Ended
Dec. 31, 2024
Summary Of Benefit Liability Recorded
The following table presents the net benefit liability/(asset) recorded on the balance sheets as of December 31, 2024 and 2023:
20242023
Ameren(a)
$(734)$(551)
Ameren Missouri(a)
(201)(142)
Ameren Illinois(a)
(438)(351)
(a)Liabilities associated with pension and other postretirement benefits are recorded in “Other current liabilities” and “Other deferred credits and liabilities” on Ameren’s, Ameren Missouri’s, and Ameren Illinois’ balance sheets.
Funded Status Of Benefit Plans and Amounts Included In Regulatory Assets and AOCI The following table presents the funded status of Ameren’s pension and postretirement benefit plans as of December 31, 2024 and 2023. It also provides the amounts included in regulatory assets or liabilities and accumulated OCI at December 31, 2024 and 2023, that have not been recognized in net periodic benefit costs.
20242023
Pension
Benefits		Postretirement
Benefits		Pension
Benefits		Postretirement
Benefits
Accumulated benefit obligation at end of year$3,962 $(a)$4,102 $(a)
Change in benefit obligation:
Net benefit obligation at beginning of year$4,258 $856 $4,061 $838 
Service cost88 12 79 12 
Interest cost222 44 221 45 
Participant contributions— 7 — 7 
Actuarial (gain) loss(143)(51)170 17 
Benefits paid(291)(61)(273)(63)
Net benefit obligation at end of year4,134 807 4,258 856 
Change in plan assets:
Fair value of plan assets at beginning of year4,272 1,393 4,027 1,249 
Actual return on plan assets193 150 514 197 
Employer contributions8 4 4 3 
Participant contributions— 7 — 7 
Benefits paid(291)(61)(273)(63)
Fair value of plan assets at end of year4,182 1,493 4,272 1,393 
Funded status – surplus(48)(686)(14)(537)
Accrued benefit asset at December 31$(48)$(686)$(14)$(537)
Amounts recognized in the balance sheet consist of:
Noncurrent asset$(71)$(686)$(44)$(537)
Current liability(b)
2 — 2 — 
Noncurrent liability(c)
21 — 28 — 
Net asset recognized$(48)$(686)$(14)$(537)
Amounts recognized in regulatory assets or liabilities consist of:
Net actuarial (gain) loss$42 $(379)$(10)$(311)
Prior service credit— (21)— (25)
Amounts recognized in accumulated OCI (pretax) consist of:
Net actuarial (gain) loss26 (7)22 (4)
Total$68 $(407)$12 $(340)
(a)Not applicable.
(b)Included in “Other current liabilities” on Ameren’s consolidated balance sheet.
(c)Included in “Other deferred credits and liabilities” on Ameren’s consolidated balance sheet.
Assumptions Used To Determine Benefit Obligations
The following table presents the assumptions used to determine our benefit obligations at December 31, 2024 and 2023:
Pension BenefitsPostretirement Benefits
2024202320242023
Discount rate at measurement date5.70 %5.25 %5.70 %5.25 %
Increase in future compensation4.00 3.50 
(a)
4.00 3.50 
(a)
Cash balance pension plan interest crediting rate5.50 5.50 (b)(b)
Medical cost trend rate (initial)(c)
(b)(b)(d)(d)
Medical cost trend rate (ultimate)(c)
(b)(b)5.00 5.00 
(a)As of December 31, 2023, increase in future compensation was 4.00% in 2024, and 3.50% thereafter.
(b)Not applicable.
(c)Initial and ultimate medical cost trend rate for certain Medicare-eligible participants was 2.50% at December 31, 2024 and 2023.
(d)Initial medical cost trend rates of 7.00% and 6.93% for pre-Medicare plan participants and 7.00% and 6.50% for post-Medicare plan participants at December 31, 2024 and 2023, respectively, trend down to the ultimate rate by 2033 and 2030, respectively, with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
Schedule Of Cash Contributions Made To Benefit Plans
The following table presents the cash contributions made to our defined benefit retirement plans and to our postretirement plan during 2024, 2023, and 2022:
Pension BenefitsPostretirement Benefits
202420232022202420232022
Ameren Missouri$1 $1 $1 $2 $2 $1 
Ameren Illinois1 2 3 1 1 1 
Ameren Services6 1 1 1 — — 
Ameren$8 $4 $5 $4 $3 $2 
Target Allocation Of The Plans' Asset Categories
The following table presents our target allocations and our pension and postretirement plans’ asset categories as of December 31, 2024 and 2023:
Asset
Category
Target Allocation
2024
Percentage of Plan Assets at December 31,
20242023
Pension Plan:
Cash and cash equivalents
0% – 5%
3 %1 %
Equity securities:
U.S. large-capitalization
10% – 20%
16 %15 %
U.S. small- and mid-capitalization
3% – 13%
9 %8 %
Global
10% – 20%
15 %16 %
International
4% – 14%
9 %12 %
Total equity
42% – 52%
49 %51 %
Debt securities
32% – 42%
35 %
(a)
35 %
(a)
Diversified credit
6% – 16%
8 %7 %
Real estate
0% – 10%
5 %6 %
Private equity
0% – 5%
(b)(b)
Total 100 %100 %
Postretirement Plans:
Cash and cash equivalents
0% – 7%
2 %1 %
Equity securities:
U.S. large-capitalization
23% – 33%
33 %32 %
U.S. small- and mid-capitalization
3% – 13%
8 %8 %
Global
9% – 19%
13 %15 %
International
5% – 15%
8 %8 %
Total equity
55% – 65%
62 %63 %
Debt securities
33% – 43%
36 %36 %
Total 100 %100 %
(a)Includes interest rate futures derivative instruments.
(b)Less than 1% of plan assets.
Components Of Net Periodic Benefit Cost
The following table presents the components of the net periodic benefit cost (income) of Ameren’s pension and postretirement benefit plans during 2024, 2023, and 2022:
Pension BenefitsPostretirement Benefits
202420232022202420232022
Service cost(a)
$88 $79 $128 $12 $12 $20 
Non-service cost components:
Interest cost222 221 163 44 45 34 
Expected return on plan assets(b)
(327)(333)(320)(93)(91)(85)
Amortization of(b):
Prior service cost (credit)— — — (4)(4)(4)
Actuarial (gain) loss(67)(115)25 (38)(45)(19)
Total non-service cost components(c)
$(172)$(227)$(132)$(91)$(95)$(74)
Net periodic benefit cost (income)(d)
$(84)$(148)$(4)$(79)$(83)$(54)
(a)Service cost, net of capitalization, is reflected in “Operating Expenses - Other operations and maintenance” on Ameren’s statement of income.
(b)Prior service cost (credit) is amortized on a straight-line basis over the average future service of active participants benefiting under the plan amendment. Net actuarial gains or losses related to the net benefit obligation subject to amortization are amortized on a straight-line basis over 10 years. The difference between the actual and expected return on plan assets is amortized over 4 years.
(c)Non-service cost components are reflected in “Other Income, Net” on Ameren’s consolidated statement of income. See Note 6 – Other Income, Net for additional information.
(d)Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in rates.
Summary Of Benefit Plan Costs Incurred
The Ameren Companies are responsible for their share of the pension and postretirement benefit costs (income). The following table presents the pension and postretirement benefit costs (income) incurred for the years ended December 31, 2024, 2023, and 2022:
Pension CostsPostretirement Costs
202420232022202420232022
Ameren Missouri(a)
$(44)$(76)$(3)$(27)$(30)$(14)
Ameren Illinois(34)(62)3 (52)(54)(41)
Other(6)(10)(4)— 1 1 
Ameren$(84)$(148)$(4)$(79)$(83)$(54)
(a)Does not include the impact of the tracker for the difference between the level of pension and postretirement benefit costs (income) incurred by Ameren Missouri under GAAP and the level of such costs included in customer rates.
Schedule Of Expected Payments From Qualified Trust And Company Funds
The expected pension and postretirement benefit payments from qualified trust and company funds, which reflect expected future service, as of December 31, 2024, are as follows:
Pension BenefitsPostretirement Benefits
Paid from
Qualified
Trust Funds		Paid from
Company
Funds		Paid from
Qualified
Trust Funds		Paid from
Company
Funds
2025$284 $2 $56 $3 
2026289 2 57 3 
2027292 2 57 4 
2028295 2 57 4 
2029297 2 57 4 
2030 – 20341,504 13 284 18 
Assumptions Used To Determine Net Periodic Benefit Cost
The following table presents the assumptions used to determine net periodic benefit cost for our pension and postretirement benefit plans for the years ended December 31, 2024, 2023, and 2022:
Pension BenefitsPostretirement Benefits
202420232022202420232022
Discount rate at measurement date5.25 %5.55 %3.00 %5.25 %5.55 %3.00 %
Expected return on plan assets6.75 6.75 6.50 6.75 6.75 6.50 
Increase in future compensation(a)
3.50 3.50 3.50 3.50 3.50 3.50 
Cash balance pension plan interest crediting rate(b)
5.50 5.00 5.00 (c)(c)(c)
Medical cost trend rate (initial)(d)
(c)(c)(c)(e)(f)5.00 
Medical cost trend rate (ultimate)(d)
(c)(c)(c)5.00 5.00 5.00 
(a)Increase in future compensation is 4.00% for 2024 and 3.50% thereafter for the year ended December 31, 2024, and was 4.50% for 2023, 4.00% for 2024, and 3.50% thereafter for the year ended December 31, 2023.
(b)Cash balance pension plan interest crediting rate is 6.42% for 2024 and 5.50% thereafter for the year ended December 31, 2024, and was 5.50% for 2023 and 2024, and 5.00% thereafter for the year ended December 31, 2023.
(c)Not applicable.
(d)Initial and ultimate medical cost trend rate for certain Medicare-eligible participants is 2.50% for the years ended December 31, 2024 and 2023, and 3.00% for the year ended December 31, 2022.
(e)Initial medical cost trend rates of 6.93% for pre-Medicare plan participants and 6.50% for post-Medicare plan participants trend down to the ultimate rate by 2030, with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
(f)Initial medical cost trend rates of 7.25% for pre-Medicare plan participants and 6.75% for post-Medicare plan participants trend down to the ultimate rate by 2030, with a 3.00% upward adjustment to the post-Medicare trend rate in 2025.
Schedule Of Matching Contributions The following table presents the portion of the matching contribution to the Ameren 401(k) plan attributable to each of the Ameren Companies for the years ended December 31, 2024, 2023, and 2022:
202420232022
Ameren Missouri$26 $27 $23 
Ameren Illinois22 21 19 
Other1 1 1 
Ameren$49 $49 $43 
Pension Benefits  
Target Allocation Of The Plans' Asset Categories
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the pension plans’ assets measured at fair value and NAV as of December 31, 2024 and 2023:
December 31, 2024December 31, 2023
Level 1Level 2NAVTotalLevel 1Level 2NAVTotal
Cash and cash equivalents$— $— $75 $75 $— $— $90 $90 
Equity securities:
U.S. large-capitalization— — 689 689 — — 663 663 
U.S. small- and mid-capitalization375 — — 375 353 — — 353 
International182 — 226 408 316 — 229 545 
Global— — 680 680 — — 721 721 
Debt securities:
Corporate bonds— 463 — 463 — 479 — 479 
Municipal bonds— 36 — 36 — 43 — 43 
U.S. Treasury and agency securities— 1,032 — 1,032 — 994 — 994 
Diversified credit— — 344 344 — — 305 305 
Other(17)11 — (6)49 13 — 62 
Real estate— — 233 233 — — 248 248 
Total$540 $1,542 $2,247 $4,329 $718 $1,529 $2,256 $4,503 
Less: Medical benefit assets(a)
(200)(196)
Plus: Net receivables (payables)(b)
53 (35)
Fair value of pension plans’ assets$4,182 $4,272 
(a)Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation.
(b)Net of receivables related to pending securities sales and payables related to pending securities purchases.
Postretirement Benefits  
Target Allocation Of The Plans' Asset Categories
The following table sets forth, by level within the fair value hierarchy discussed in Note 8 – Fair Value Measurements, the postretirement benefit plans’ assets measured at fair value and NAV as of December 31, 2024 and 2023:
December 31, 2024December 31, 2023
Level 1Level 2NAVTotalLevel 1Level 2NAVTotal
Cash and cash equivalents$25 $— $— $25 $10 $— $— $10 
Equity securities:
U.S. large-capitalization332 — 91 423 302 — 81 383 
U.S. small- and mid-capitalization106 — — 106 96 — — 96 
International54 — 52 106 51 — 49 100 
Global— — 165 165 — — 174 174 
Debt securities:
Municipal bonds— 173 — 173 — 161 — 161 
Other— — 293 293 — — 271 271 
Total$517 $173 $601 $1,291 $459 $161 $575 $1,195 
Plus: Medical benefit assets(a)
200 196 
Plus: Net receivables(b)
  2 2 
Fair value of postretirement benefit plans’ assets  $1,493 $1,393 
(a)Medical benefit (health and welfare) component for accounts maintained in accordance with Section 401(h) of the Internal Revenue Code to fund a portion of the postretirement obligation. These 401(h) assets are included in the pension plan assets shown above.
(b)Net of receivables related to pending securities sales and payables related to pending securities purchases.