The Corporation has a noncontributory defined benefit RAP, covering substantially all employees who meet participation requirements. The benefit allocations are based primarily on years of service and the employee’s compensation paid. Employees of acquired entities generally participate in the RAP after consummation of the business combinations. Any retirement plans of acquired entities are typically merged into the RAP after completion of the mergers, and credit is usually given to employees for years of service at the acquired institution for vesting and eligibility purposes.

The Corporation also provides legacy healthcare access to a limited group of retired employees from a previous acquisition in the Postretirement Plan. There are no other active retiree healthcare plans.

The funded status and amounts recognized on the 2025 and 2024 consolidated balance sheets for the RAP and Postretirement Plan were as follows:


	RAP		Postretirement Plan		RAP		Postretirement Plan
(in thousands)	2025		2025		2024		2024
Change in fair value of plan assets
Fair value of plan assets at beginning of year	$	478,970	$	—	$	453,457	$	—
Actual return on plan assets	55,988		—		43,676		—
Employer contributions	—		190		—		183
Benefits paid	(17,379)		(190)		(18,163)		(183)
Fair value of plan assets at end of year(a)	$	517,579	$	—	$	478,970	$	—
Change in benefit obligation
Net benefit obligation at beginning of year	$	213,365	$	2,043	$	211,353	$	1,425
Service cost	3,007		—		3,027		—
Interest cost	11,540		105		11,173		73

Actuarial loss (gain)	8,250		(248)		5,975		729
Benefits paid	(17,379)		(190)		(18,163)		(183)

Net benefit obligation at end of year(a)	$	218,783	$	1,710	$	213,365	$	2,043
Funded (unfunded) status	$	298,796	$	(1,710)	$	265,605	$	(2,043)
Noncurrent assets	$	298,796	$	—	$	265,605	$	—
Current liabilities	—		(185)		—		(212)
Noncurrent liabilities	—		(1,525)		—		(1,832)
Asset (liability) recognized on the consolidated balance sheets	$	298,796	$	(1,710)	$	265,605	$	(2,043)

(a) The fair value of the plan assets represented 237% and 224% of the net benefit obligation of the RAP at December 31, 2025 and 2024, respectively.

Amounts recognized in accumulated other comprehensive (income) loss, net of tax, were as follows:


	RAP		Postretirement Plan		RAP		Postretirement Plan
(in thousands)	2025		2025		2024		2024
Prior service cost	$	(590)	$	(196)	$	(723)	$	(252)
Net actuarial loss	14,820		69		24,758		267
Amount not yet recognized in net periodic benefit cost, but recognized in accumulated other comprehensive loss (income)	$	14,230	$	(127)	$	24,035	$	15

Other changes in plan assets and benefit obligations recognized in OCI, net of tax were as follows:


	RAP		Postretirement Plan		RAP		Postretirement Plan
(in thousands)	2025		2025		2024		2024
Net actuarial gain (loss)	$	8,472	$	248	$	3,102	$	(729)
Amortization of prior service cost	(177)		(75)		(215)		(75)
Amortization of actuarial gain	—		(16)		—		(28)

Income tax (expense) benefit	(2,070)		(47)		(718)		208
Total recognized in OCI	$	6,225	$	110	$	2,169	$	(624)

The components of net periodic pension benefit cost for the RAP were as follows:


(in thousands)	2025		2024		2023
Service cost	$	3,007	$	3,027	$	3,189
Interest cost	11,540		11,173		10,887
Expected return on plan assets	(39,267)		(34,599)		(32,862)
Amortization of prior service cost	(177)		(215)		(250)
Amortization of actuarial loss	—		—		—

Total net periodic pension benefit income	$	(24,897)	$	(20,614)	$	(19,037)

The components of net periodic benefit cost for the Postretirement Plan were as follows:


(in thousands)	2025		2024		2023
Interest cost	$	105	$	73	$	78
Amortization of prior service cost	(75)		(75)		(75)
Amortization of actuarial loss (gain)	16		(28)		(29)
Total net periodic benefit cost (income)	$	46	$	(31)	$	(26)

The components of net periodic pension cost and net periodic benefit cost, other than the service cost component, are included in the other noninterest expense caption of the consolidated statements of income. The service cost components are included in the personnel noninterest expense caption of the consolidated statements of income.


	RAP		Postretirement Plan		RAP		Postretirement Plan
	2025		2025		2024		2024
Weighted average assumptions used to determine benefit obligations
Discount rate	5.30	%	5.30	%	5.40	%	5.40	%
Rate of increase in compensation levels	3.00	%	N/A		2.50	%	N/A
Interest crediting rate	3.75	%	N/A		3.81	%	N/A
Weighted average assumptions used to determine net periodic benefit costs
Discount rate	5.70	%	5.40	%	5.40	%	5.40	%
Rate of increase in compensation levels	2.50	%	N/A		2.50	%	N/A
Expected long-term rate of return on plan assets	8.20	%	N/A		7.40	%	N/A

The expected long-term rate of return on plan assets was estimated based on the RAP's current mix of the plan assets and a forward looking capital markets model which estimates long-term future returns. This model estimates expected long-term, forward-looking, annual returns and expected annual volatilities for different asset classes and correlations between each asset class pair using current yields for investment grade fixed income securities and risk premiums for riskier asset classes. The actual rates of return for the RAP assets were 12.54% and 10.16% for 2025 and 2024, respectively.

The RAP’s investments are exposed to various risks, such as interest rate, market, and credit risks. Due to the level of risks associated with certain investments and the level of uncertainty related to changes in the value of the investments, it is at least reasonably possible that changes in risks in the near term could materially affect the amounts reported. The investment objective for the RAP is to ensure there are sufficient assets to pay pension obligations when they come due while mitigating risks and providing prudent governance. The RAP has a diversified portfolio designed to provide liquidity, current income, and growth of income and principal, with anticipated asset allocation ranges of: equity securities 50 to 70%, fixed-income securities 30 to 50%, alternative securities 0 to 15%, and other cash equivalents 0 to 5%. Based on changes in economic and market conditions, the Corporation could be outside of the allocation ranges for brief periods of time. The asset allocation for the RAP as of the December 31, 2025 and 2024 measurement dates, respectively, by asset category were as follows:


Asset Category	2025		2024
Equity securities	56	%	55	%
Fixed-income securities	35	%	35	%
Group annuity contracts	8	%	8	%

Other	1	%	2	%
Total	100	%	100	%

The RAP assets include cash equivalents, such as money market accounts, mutual funds, common / collective trust funds (which include investments in equity and bond securities), and a group annuity contract. Money market accounts are stated at cost plus accrued interest, mutual funds are valued at quoted market prices, investments in common / collective trust funds are

valued at the amount at which units in the funds can be withdrawn, and the group annuity contract is valued at fair value by discounting the related cash flows based on current yields of similar instruments with comparable durations and considering the credit worthiness of the issuer.

Based on these inputs, the following tables summarize the fair value of the RAP’s investments:


	December 31, 2025
(in thousands)	Fair Value		Level 1		Level 2		Level 3
RAP investments
Money market account	$	2,661	$	2,661	$	—	$	—
Common /collective trust funds	197,772		197,772		—		—
Mutual funds	277,577		277,577		—		—
Group annuity contract	39,569		—		—		39,569
Total RAP investments	$	517,579	$	478,010	$	—	$	39,569

	December 31, 2024
(in thousands)	Fair Value		Level 1		Level 2		Level 3
RAP investments
Money market account	$	7,892	$	7,892	$	—	$	—
Common /collective trust funds	183,059		183,059		—		—
Mutual funds	247,602		247,602		—		—
Group annuity contract	40,416		—		—		40,416
Total RAP investments	$	478,970	$	438,554	$	—	$	40,416

The following presents a summary of the changes in the fair value of the RAP's Level 3 asset during the periods indicated.


Fair Value Reconciliation of Level 3 RAP Investments	2025		2024
Fair value of group annuity contract at beginning of period	$	40,416	$	43,687
Return on plan assets	1,645		(731)

Benefits paid	(2,492)		(2,539)
Fair value of group annuity contract at end of period	$	39,569	$	40,416

The Corporation’s RAP funding policy is to pay at least the minimum amount required by federal law and regulations, with consideration given to the maximum funding amounts allowed. The Corporation regularly reviews the funding of its RAP. There were no contributions to the RAP during 2025 and 2024.

The projected benefit payments were calculated using the same assumptions as those used to calculate the benefit obligations listed above. The projected benefit payments for the RAP and Postretirement Plan at December 31, 2025, reflecting expected future services, were as follows:


(in thousands)	RAP		Postretirement Plan
Estimated future benefit payments
2026	$	22,872	$	190
2027	21,660		185
2028	21,472		179
2029	21,555		173
2030	21,226		166
2031-2035	85,207		711

The health care trend rate is an assumption as to how much the Postretirement Plan’s medical costs will change each year in the future. There are no remaining participants under age 65 in the Postretirement Plan. The actual change in 2025 health care premium rates for post-65 coverage was a decrease of 47.66%. The health care trend rate assumption for post-65 coverage assumes a 5.80% rate of increase for 2026, declining to an ultimate trend rate of 5% by the year 2030.

The Corporation also has a 401(k) and Employee Stock Ownership Plan (the “401(k) plan”). The Corporation’s contribution is determined by the Compensation and Benefits Committee of the Board of Directors. Total expenses related to contributions to the 401(k) plan were $17.5 million, $17.2 million, and $15.6 million for 2025, 2024, and 2023, respectively.

Standby Letters of Credit [Member]

Lending Related Commitments

asb_LendingRelatedCommitments

$ 222,000,000.0

Lending Related Commitments

asb_LendingRelatedCommitments

253,700,000

Fair Value Hedging [Member] | Interest Expense [Member]

Increase (Decrease) in Fair Value of Hedged Item in Interest Rate Fair Value Hedge

us-gaap_IncreaseDecreaseInFairValueOfHedgedItemInInterestRateFairValueHedge1

(12,222,000)

Increase (Decrease) in Fair Value of Hedged Item in Interest Rate Fair Value Hedge