Commitments, Contingencies and Guarantees - Additional Information (Detail) - USD ($) |
3 Months Ended | 6 Months Ended | |||||
|---|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Jun. 30, 2026 |
Jun. 30, 2025 |
Mar. 31, 2026 |
Dec. 31, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
|
| Commitments and Contingencies Disclosure [Line Items] | |||||||
| ACL for off-balance sheet credit exposures | $ 5,721,000 | $ 5,721,000 | $ 8,221,000 | $ 5,721,000 | $ 5,721,000 | $ 8,221,000 | $ 4,138,000 |
| Provision for off-balance sheet credit exposures | 0 | 0 | $ 500,000 | ||||
| Heartland Financial USA, Inc [Member] | |||||||
| Commitments and Contingencies Disclosure [Line Items] | |||||||
| ACL for off-balance sheet credit exposures | 3,600,000 | 3,600,000 | |||||
| Accrued Expenses and Taxes [Member] | |||||||
| Commitments and Contingencies Disclosure [Line Items] | |||||||
| ACL for off-balance sheet credit exposures | $ 5,700,000 | $ 5,700,000 | |||||