Loans and Allowance for Credit Losses - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2025 USD ($) Loan	Mar. 31, 2024 USD ($) Loan	Jan. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Loan portfolio purchases included in credit card receivables		$ 109,400,000
Proceeds from sales of loans held for sale	$ 16,389,000	18,399,000
Nonaccrual Loans	100,885,000			$ 19,282,000
Restructured loans	189,000			196,000
Total Past Due	35,936,281,000			25,642,301,000
Non accrual loans with no related allowance for credit losses	100,885,000			19,282,000
Accrued interest on loans	$ 175,200,000			125,700,000
Credit card payments delinquency period beyond which payments considered significantly delinquent	60 days
Number of reasonable and supportable forecast period	1 year
Modifications made to borrowers experiencing financial difficulty commitment to lend	$ 0	$ 0
Loan modifications made to borrowers experiencing financial difficulty | Loan	0	0
Residential Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Financing receivable modifications number of contracts | Loan	1	0
Pre- and post-modification loan balance	$ 225,000
Consumer Real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Proceeds from sales of loans held for sale	$ 16,400,000	$ 18,400,000
Heartland Financial USA Inc [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Fair value of loans acquired net of allowance for credit losses			$ 9,800,000,000
Minimum [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Number of reasonable and supportable forecast period	1 year
Maximum [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Number of reasonable and supportable forecast period	3 years
Greater than 90 days Past Due and Accruing [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Total Past Due	$ 6,346,000			$ 7,602,000