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Investment Securities - Mortgage-backed Asset Securities Table (Details) - USD ($) $ in Millions | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | $ 273.6 | $ 231.9
Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 14.4 | 22.3
Total mortgage and asset-backed securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 288.0 | 254.2
Collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 187.8 | 182.9
Total mortgage and asset-backed securities and collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 475.8 | 437.1
Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 273.6 | 231.9
Level 2 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 14.4 | 22.3
Level 2 | Total mortgage and asset-backed securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 288.0 | 254.2
Level 2 | Collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 187.8 | 182.9
Level 2 | Total mortgage and asset-backed securities and collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 475.8 | 437.1
Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Level 3 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Level 3 | Total mortgage and asset-backed securities |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Level 3 | Collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Level 3 | Total mortgage and asset-backed securities and collateralized loan obligations |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
FNMA | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 155.6 | 124.5
FNMA | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 155.6 | 124.5
FNMA | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
FHLMC | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 86.2 | 78.8
FHLMC | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 86.2 | 78.8
FHLMC | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
GNMA | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 31.6 | 28.3
GNMA | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 31.6 | 28.3
GNMA | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Non-agency: Residential | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.2 | 0.3
Non-agency: Residential | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.2 | 0.3
Non-agency: Residential | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Total non-agency | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.2 | 0.3
Total non-agency | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.2 | 0.3
Total non-agency | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Credit card receivables | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 3.2 | 11.9
Credit card receivables | Level 2 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 3.2 | 11.9
Credit card receivables | Level 3 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Vehicle receivables | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 11.2 | 10.4
Vehicle receivables | Level 2 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 11.2 | 10.4
Vehicle receivables | Level 3 | Other asset-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 0.0 | 0.0
Collateralized mortgage obligations | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 187.8 |
Total agency | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 273.4 | 231.6
Total agency | Level 2 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | 273.4 | 231.6
Total agency | Level 3 | Mortgage-backed securities: |  |
Debt and Equity Securities, FV-NI [Line Items] |  |
Fair value investments | $ 0.0 | $ 0.0

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