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Investment Securities - Credit Quality Indicators (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021
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Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | $ 3,453.7 | $ 1,687.6
AAA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 3,260.7 | 1,626.2
AA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 92.8 | 31.6
A Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 11.5 | 18.7
BBB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 65.1 | 7.0
BB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 10.0 |
Not Rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 13.6 | 4.1
US Treasury Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 396.6 |
US Treasury Securities [Member] | AAA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 396.6 |
US Treasury Securities [Member] | AA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Treasury Securities [Member] | A Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Treasury Securities [Member] | BBB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Treasury Securities [Member] | BB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Treasury Securities [Member] | Not Rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
State, county and municipal securities |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 181.2 | 67.6
State, county and municipal securities | AAA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 68.3 | 17.2
State, county and municipal securities | AA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 92.8 | 31.6
State, county and municipal securities | A Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 11.5 | 14.7
State, county and municipal securities | BBB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
State, county and municipal securities | BB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
State, county and municipal securities | Not Rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 8.6 | 4.1
US Government Agencies Debt Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 351.7 |
US Government Agencies Debt Securities [Member] | AAA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 351.7 |
US Government Agencies Debt Securities [Member] | AA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Government Agencies Debt Securities [Member] | A Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Government Agencies Debt Securities [Member] | BBB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Government Agencies Debt Securities [Member] | BB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
US Government Agencies Debt Securities [Member] | Not Rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 2,444.1 | 1,609.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 2,233.6 | 1,439.1
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 210.5 | 169.9
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | AAA Rating | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 2,233.6 | 1,439.1
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | AAA Rating | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 210.5 | 169.9
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | AA Rating | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | AA Rating | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | A Rating | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | A Rating | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | BBB Rating | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | BBB Rating | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | BB Rating | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | BB Rating | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 |
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Not Rated | FNMA and FHLMC |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Not Rated | GNMA |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Corporate Debt Securities [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 80.1 | 11.0
Corporate Debt Securities [Member] | AAA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Corporate Debt Securities [Member] | AA Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 0.0
Corporate Debt Securities [Member] | A Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 0.0 | 4.0
Corporate Debt Securities [Member] | BBB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 65.1 | 7.0
Corporate Debt Securities [Member] | BB Rating |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | 10.0 |
Corporate Debt Securities [Member] | Not Rated |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Debt Securities, Held-to-maturity | $ 5.0 | $ 0.0

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