Subordinated Debentures Held by Subsidiary Trusts (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) trusts	Dec. 31, 2023 USD ($)	May 31, 2020	Nov. 01, 2007	Jun. 22, 2005
Subordinated Borrowing
Number of company sponsored wholly-owned business trusts | trusts	14
Stated interest rate	4.77%	5.52%	5.25%
Subordinated Debt	$ 163.7	$ 163.7
Subordinated Long-term Debt, Noncurrent		163.1
Common Stock Held in Assets	5.3	5.3
Subordinated Debt Fair Value Adjustment	(0.6)	(0.6)
Subordinated debentures held by subsidiary trusts	163.1	163.1
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust II
Subordinated Borrowing
Subordinated Debt	2.0
Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I
Subordinated Borrowing
Subordinated Debt	5.0
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust VI
Subordinated Borrowing
Subordinated Debt	30.0
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust IV
Subordinated Borrowing
Subordinated Debt	22.4
Junior Subordinated Deferrable Interest Debentures Issued by HFFC III
Subordinated Borrowing
Subordinated Debt	5.0
Junior Subordinated Deferrable Interest Debentures Issued by HFFC IV
Subordinated Borrowing
Subordinated Debt	7.0
Junior Subordinated Deferrable Interest Debentures Issued by HFFC V
Subordinated Borrowing
Subordinated Debt	5.0
Junior Subordinated Deferrable Interest Debentures Issued by HFFC VI
Subordinated Borrowing
Subordinated Debt	2.0
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust II
Subordinated Borrowing
Common Stock Held in Assets	$ 0.1	0.1
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust II | Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust II
Subordinated Borrowing
Debt instrument, interest rate at period end	6.47%
Subordinated Debt	$ 2.1	2.1
Debt instrument, basis spread on variable rate	1.85%
Junior Subordinated Deferrable Interest Debentures Issued by FIST II
Subordinated Borrowing
Common Stock Held in Assets	$ 0.3	0.3
Junior Subordinated Deferrable Interest Debentures Issued by FIST II | Junior Subordinated Deferrable Interest Debentures Issued by FIST II
Subordinated Borrowing
Debt instrument, interest rate at period end	7.10%
Subordinated Debt	$ 10.3	10.3
Debt instrument, basis spread on variable rate	2.25%
Junior Subordinated Deferrable Interest Debentures Issued by FIST I
Subordinated Borrowing
Common Stock Held in Assets	$ 0.5	0.5
Junior Subordinated Deferrable Interest Debentures Issued by FIST I | Junior Subordinated Deferrable Interest Debentures Issued by FIST I
Subordinated Borrowing
Debt instrument, interest rate at period end	7.37%
Subordinated Debt	$ 15.5	15.5
Junior Subordinated Deferrable Interest Debentures Issued by FIST I | Junior Subordinated Deferrable Interest Debentures Issued by FIST I | Debt Instrument, Redemption, After Period Five
Subordinated Borrowing
Debt instrument, basis spread on variable rate	2.75%
Junior Subordinated Deferrable Interest Debentures Issued by FIST I | Junior Subordinated Deferrable Interest Debentures Issued by FIST I | Debt Instrument, Redemption, At Issuance through Year Five [Member]
Subordinated Borrowing
Stated interest rate				7.50%
Junior Subordinated Deferrable Interest Debentures Issued by FIST III
Subordinated Borrowing
Common Stock Held in Assets	$ 0.6	0.6
Junior Subordinated Deferrable Interest Debentures Issued by FIST III | Junior Subordinated Deferrable Interest Debentures Issued by FIST III
Subordinated Borrowing
Debt instrument, interest rate at period end	7.02%
Subordinated Debt	$ 20.6	20.6
Junior Subordinated Deferrable Interest Debentures Issued by FIST III | Junior Subordinated Deferrable Interest Debentures Issued by FIST III | Debt Instrument, Redemption, After Period Five
Subordinated Borrowing
Debt instrument, basis spread on variable rate	2.40%
Junior Subordinated Deferrable Interest Debentures Issued by FIST III | Junior Subordinated Deferrable Interest Debentures Issued by FIST III | Debt Instrument, Redemption, At Issuance through Year Five [Member]
Subordinated Borrowing
Stated interest rate					6.88%
Junior Subordinated Deferrable Interest Debentures Issued by FIST IV
Subordinated Borrowing
Common Stock Held in Assets	$ 0.5	0.5
Junior Subordinated Deferrable Interest Debentures Issued by FIST IV | Junior Subordinated Deferrable Interest Debentures Issued by FIST IV
Subordinated Borrowing
Debt instrument, interest rate at period end	7.55%
Subordinated Debt	$ 15.5	15.5
Debt instrument, basis spread on variable rate	2.70%
Junior Subordinated Deferrable Interest Debentures Issued by FIST V
Subordinated Borrowing
Common Stock Held in Assets	$ 0.3	0.3
Junior Subordinated Deferrable Interest Debentures Issued by FIST V | Junior Subordinated Deferrable Interest Debentures Issued by FIST V
Subordinated Borrowing
Debt instrument, interest rate at period end	7.60%
Subordinated Debt	$ 10.3	10.3
Junior Subordinated Deferrable Interest Debentures Issued by FIST V | Junior Subordinated Deferrable Interest Debentures Issued by FIST V | Debt Instrument, Redemption, After Period Five
Subordinated Borrowing
Debt instrument, basis spread on variable rate	2.75%
Junior Subordinated Deferrable Interest Debentures Issued by FIST V | Junior Subordinated Deferrable Interest Debentures Issued by FIST V | Debt Instrument, Redemption, At Issuance through Year Five [Member]
Subordinated Borrowing
Stated interest rate					6.78%
Junior Subordinated Deferrable Interest Debentures Issued by FIST VI
Subordinated Borrowing
Common Stock Held in Assets	$ 0.3	0.3
Junior Subordinated Deferrable Interest Debentures Issued by FIST VI | Junior Subordinated Deferrable Interest Debentures Issued by FIST VI
Subordinated Borrowing
Debt instrument, interest rate at period end	7.60%
Subordinated Debt	$ 10.3	10.3
Debt instrument, basis spread on variable rate	2.75%
Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I
Subordinated Borrowing
Common Stock Held in Assets	$ 0.2	0.2
Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I | Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I
Subordinated Borrowing
Debt instrument, interest rate at period end	6.29%
Subordinated Debt	$ 5.2	5.2
Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I | Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I | Debt Instrument, Redemption, After Period Five
Subordinated Borrowing
Debt instrument, basis spread on variable rate	1.70%
Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I | Junior Subordinated Deferrable Interest Debentures Issued by INB Cap Trust I | Debt Instrument, Redemption, At Issuance through Year Five [Member]
Subordinated Borrowing
Stated interest rate					5.95%
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust VI
Subordinated Borrowing
Common Stock Held in Assets	$ 0.9	0.9
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust VI | Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust VI
Subordinated Borrowing
Debt instrument, interest rate at period end	6.10%
Subordinated Debt	$ 30.9	30.9
Debt instrument, basis spread on variable rate	1.48%
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust IV
Subordinated Borrowing
Common Stock Held in Assets	$ 0.7	0.7
Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust IV | Junior Subordinated Deferrable Interest Debentures Issued by GWB Trust IV
Subordinated Borrowing
Debt instrument, interest rate at period end	7.46%
Subordinated Debt	$ 23.1	23.1
Debt instrument, basis spread on variable rate	2.85%
Junior Subordinated Deferrable Interest Debentures Issued by HFFC III
Subordinated Borrowing
Common Stock Held in Assets	$ 0.2	0.2
Junior Subordinated Deferrable Interest Debentures Issued by HFFC III | Junior Subordinated Deferrable Interest Debentures Issued by HFFC III
Subordinated Borrowing
Debt instrument, interest rate at period end	8.27%
Subordinated Debt	$ 5.2	5.2
Debt instrument, basis spread on variable rate	3.35%
Junior Subordinated Deferrable Interest Debentures Issued by HFFC IV
Subordinated Borrowing
Common Stock Held in Assets	$ 0.2	0.2
Junior Subordinated Deferrable Interest Debentures Issued by HFFC IV | Junior Subordinated Deferrable Interest Debentures Issued by HFFC IV
Subordinated Borrowing
Debt instrument, interest rate at period end	8.02%
Subordinated Debt	$ 7.2	7.2
Debt instrument, basis spread on variable rate	3.10%
Junior Subordinated Deferrable Interest Debentures Issued by HFFC V
Subordinated Borrowing
Common Stock Held in Assets	$ 0.3	0.3
Junior Subordinated Deferrable Interest Debentures Issued by HFFC V | Junior Subordinated Deferrable Interest Debentures Issued by HFFC V
Subordinated Borrowing
Debt instrument, interest rate at period end	6.59%
Subordinated Debt	$ 5.3	5.3
Debt instrument, basis spread on variable rate	1.83%
Junior Subordinated Deferrable Interest Debentures Issued by HFFC VI
Subordinated Borrowing
Common Stock Held in Assets	$ 0.2	0.2
Junior Subordinated Deferrable Interest Debentures Issued by HFFC VI | Junior Subordinated Deferrable Interest Debentures Issued by HFFC VI
Subordinated Borrowing
Debt instrument, interest rate at period end	6.50%
Subordinated Debt	$ 2.2	$ 2.2
Debt instrument, basis spread on variable rate	1.65%
Trust Preferred Securities Subject to Mandatory Redemption | Trusts
Subordinated Borrowing
Business trust term (in years)	30 years
Common Stock Subject to Mandatory Redemption | Trusts
Subordinated Borrowing
Amount of financial instruments subject to mandatory redemption	$ 5.3
Subordinated Debentures Subject to Mandatory Redemption | Trusts
Subordinated Borrowing
Business trust term (in years)	30 years