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Borrowings - Narrative (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Schedule Of Short Term And Long Term Debt [Line Items] |  |
FHLB advances | $ 2,090.0 |
Unencumbered securities | 647.5 |
Multifamily loans held as collateral | 1,440.0 |
Repurchase agreements | Mortgage-backed securities |  |
Schedule Of Short Term And Long Term Debt [Line Items] |  |
Mortgage-backed securities amortized cost | 52.6 | $ 88.9
Mortgage-backed securities held for sale fair value | $ 53.8 | $ 91.4

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