Borrowed Funds - Summary of Outstanding Trust Preferred Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Amount Outstanding	$ 654,380	$ 385,292
Trust Preferred Securities [Member]
Debt Instrument [Line Items]
Amount Outstanding	216,826	$ 76,782
Trust Preferred Securities [Member] | Marquette Capital Trust I [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 19,017
Issuance Date	Dec. 28, 2005
Interest Rate	1.33% over 3-month term SOFR
Interest Rate as of March 31, 2025	5.89%
Maturity Date	Jan. 07, 2036
Trust Preferred Securities [Member] | Marquette Capital Trust II [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 19,513
Issuance Date	Dec. 28, 2005
Interest Rate	1.33% over 3-month term SOFR
Interest Rate as of March 31, 2025	5.89%
Maturity Date	Jan. 07, 2036
Trust Preferred Securities [Member] | Marquette Capital Trust III [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 7,663
Issuance Date	May 30, 2006
Interest Rate	1.50% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.06%
Maturity Date	Jun. 23, 2036
Trust Preferred Securities [Member] | Marquette Capital Trust IV [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 30,922
Issuance Date	Jun. 30, 2006
Interest Rate	1.60% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.16%
Maturity Date	Sep. 15, 2036
Trust Preferred Securities [Member] | Heartland Financial Statutory Trust IV [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 9,538
Issuance Date	Mar. 17, 2004
Interest Rate	2.75% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.31%
Maturity Date	Mar. 17, 2034
Trust Preferred Securities [Member] | Heartland Financial Statutory Trust V [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 17,141
Issuance Date	Jan. 27, 2006
Interest Rate	1.33% over 3-month term SOFR
Interest Rate as of March 31, 2025	5.89%
Maturity Date	Apr. 07, 2036
Trust Preferred Securities [Member] | Heartland Financial Statutory Trust VI [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 16,660
Issuance Date	Jun. 21, 2007
Interest Rate	1.48% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.04%
Maturity Date	Sep. 15, 2037
Trust Preferred Securities [Member] | Heartland Financial Statutory Trust VII [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 14,577
Issuance Date	Jun. 26, 2007
Interest Rate	1.48% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.06%
Maturity Date	Sep. 01, 2037
Trust Preferred Securities [Member] | Morrill Statutory Trust I [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 9,854
Issuance Date	Dec. 19, 2002
Interest Rate	3.25% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.81%
Maturity Date	Dec. 26, 2032
Trust Preferred Securities [Member] | Morrill Statutory Trust II [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 9,604
Issuance Date	Dec. 17, 2003
Interest Rate	2.85% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.41%
Maturity Date	Dec. 17, 2033
Trust Preferred Securities [Member] | Sheboygan Statutory Trust I [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 7,253
Issuance Date	Sep. 17, 2003
Interest Rate	2.95% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.51%
Maturity Date	Sep. 17, 2033
Trust Preferred Securities [Member] | CBNM Capital Trust I [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 4,803
Issuance Date	Sep. 10, 2004
Interest Rate	3.25% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.81%
Maturity Date	Dec. 15, 2034
Trust Preferred Securities [Member] | Citywide Capital Trust III [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 6,711
Issuance Date	Dec. 19, 2003
Interest Rate	2.80% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.35%
Maturity Date	Dec. 19, 2033
Trust Preferred Securities [Member] | Citywide Capital Trust IV [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 4,618
Issuance Date	Sep. 30, 2004
Interest Rate	2.20% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.79%
Maturity Date	Sep. 30, 2034
Trust Preferred Securities [Member] | Citywide Capital Trust V [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 12,892
Issuance Date	May 31, 2006
Interest Rate	1.54% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.10%
Maturity Date	Jul. 25, 2036
Trust Preferred Securities [Member] | OCGI Statutory Trust III [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 2,993
Issuance Date	Jun. 27, 2002
Interest Rate	3.65% over 3-month term SOFR
Interest Rate as of March 31, 2025	8.21%
Maturity Date	Sep. 30, 2032
Trust Preferred Securities [Member] | OCGI Statutory Trust IV [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 5,586
Issuance Date	Sep. 23, 2004
Interest Rate	2.50% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.06%
Maturity Date	Dec. 15, 2034
Trust Preferred Securities [Member] | BVBC Capital Trust II [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 7,366
Issuance Date	Apr. 10, 2003
Interest Rate	3.25% over 3-month term SOFR
Interest Rate as of March 31, 2025	7.80%
Maturity Date	Apr. 24, 2033
Trust Preferred Securities [Member] | BVBC Capital Trust III [Member]
Debt Instrument [Line Items]
Amount Outstanding	$ 10,115
Issuance Date	Jul. 29, 2005
Interest Rate	1.60% over 3-month term SOFR
Interest Rate as of March 31, 2025	6.16%
Maturity Date	Sep. 30, 2035