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Derivatives and Hedging Activities - Notional Amounts and Estimated Fair Values of Derivatives (Details) $ in Millions | Dec. 31, 2020 USD ($) | May 01, 2020 USD ($) | Dec. 31, 2019 USD ($)
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Derivative [Line Items] |  |  |
Derivative Asset, Notional Amount | $ 901.6 |  | $ 571.0
Derivative Assets, Estimated Fair Value | 55.3 |  | 23.2
Derivative Liability, Notional Amount | 1,014.1 |  | 631.2
Derivative Liabilities, Estimated Fair Value | 53.3 |  | 22.2
Interest Rate Cash Flow Hedge Derivative at Fair Value, Net | 0.0 |  |
Interest Rate Swap |  |  |
Derivative [Line Items] |  |  |
Derivative Liability, Notional Amount |  | $ 46.4 |
Derivative, Notional Amount, Contract 2 |  | 36.1 |
Derivative, Notional Amount, Contract 3 |  | $ 5.1 |
Derivative, Fixed Interest Rate, Contract 1 |  | 0.0040 |
Derivative, Fixed Interest Rate, Contract 2 |  | 0.0034 |
Derivative, Fixed Interest Rate, Contract 3 |  | 0.0040 |
Not Designated as Hedging Instrument | Interest Rate Swap |  |  |
Derivative [Line Items] |  |  |
Derivative Asset, Notional Amount | 799.7 |  | 503.2
Derivative Assets, Estimated Fair Value | 52.0 |  | 21.9
Derivative Liability, Notional Amount | 799.7 |  | 503.2
Derivative Liabilities, Estimated Fair Value | 52.0 |  | 21.9
Not Designated as Hedging Instrument | Interest rate lock commitments |  |  |
Derivative [Line Items] |  |  |
Derivative Asset, Notional Amount | 101.9 |  | 67.8
Derivative Assets, Estimated Fair Value | 3.3 |  | 1.3
Not Designated as Hedging Instrument | Forward loan sales contracts |  |  |
Derivative [Line Items] |  |  |
Derivative Liability, Notional Amount | 126.8 |  | 128.0
Derivative Liabilities, Estimated Fair Value | 1.1 |  | 0.3
Designated as Hedging Instrument | Interest Rate Swap |  |  |
Derivative [Line Items] |  |  |
Derivative Asset, Notional Amount | 87.6 |  | 0.0
Derivative Assets, Estimated Fair Value | $ 0.2 |  | $ 0.0

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