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Commitments, Contingencies and Guarantees - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Jan. 31, 2025	Dec. 31, 2024	Jun. 30, 2024	Dec. 31, 2023
Commitments and Contingencies Disclosure [Line Items]
ACL for off-balance sheet credit exposures	$ 7,721,000	$ 4,138,000	$ 7,721,000	$ 4,138,000	$ 8,221,000		$ 4,138,000	$ 4,138,000	$ 5,088,000
Provision for off-balance sheet credit exposures	(500,000)	$ 0	0	$ (950,000)
Heartland Financial USA, Inc [Member]
Commitments and Contingencies Disclosure [Line Items]
ACL for off-balance sheet credit exposures						$ 3,600,000
Accrued Expenses and Taxes [Member]
Commitments and Contingencies Disclosure [Line Items]
ACL for off-balance sheet credit exposures	$ 7,700,000		$ 7,700,000				$ 4,100,000

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- Definition

Commitments and contingencies disclosure.

+ References

No definition available.

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Amount of expected credit loss for credit exposure on off-balance-sheet commitment, including but not limited to, loan commitment, standby letter of credit, financial guarantee not accounted for as insurance. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482454/460-10-45-1

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Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-22

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