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Derivatives and Hedging Activities - Schedule of Master Netting Arrangements (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020
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Derivative Asset [Abstract] |  |
Derivative Asset, Fair Value, Gross Asset | $ 28.1 | $ 55.3
Derivative Asset, Fair Value, Gross Liability | 0.0 | 0.0
Derivative Asset, Total | 28.1 | 55.3
Derivative, Collateral, Obligation to Return Securities | 0.0 | 0.0
Derivative, Collateral, Obligation to Return Cash | 8.0 | 17.2
Derivative Asset, Fair Value, Amount Offset Against Collateral, Total | 20.1 | 38.1
Offsetting Derivative Liabilities [Abstract] |  |
Derivative Liability, Fair Value, Gross Liability | 18.2 | 17.9
Derivative Liability, Fair Value, Gross Asset | 0.0 | 0.0
Derivative Liability, Total | 18.2 | 17.9
Derivative, Collateral, Right to Reclaim Securities | 0.0 | 0.0
Derivative, Collateral, Right to Reclaim Cash | 0.0 | 0.0
Derivative Liability, Fair Value, Amount Offset Against Collateral, Total | 18.2 | 17.9
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral [Abstract] |  |
Securities Sold under Agreements to Repurchase, Gross | 1,051.1 | 1,091.4
Securities Sold under Agreements to Repurchase, Asset | 0.0 | 0.0
Securities Sold under Agreements to Repurchase, Total | 1,051.1 | 1,091.4
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities | 0.0 | 0.0
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Cash | 1,051.1 | 1,091.4
Securities Sold under Agreements to Repurchase, Amount Offset Against Collateral, Total | 0.0 | 0.0
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] |  |
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Gross | 1,069.3 | 1,109.3
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Asset | 0.0 | 0.0
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Total | 1,069.3 | 1,109.3
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Securities | 0.0 | 0.0
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Collateral, Right to Reclaim Cash | 1,051.1 | 1,091.4
Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned, Amount Offset Against Collateral, Total | 18.2 | 17.9
Derivative Asset, Notional Amount | 1,691.2 | 901.6
Derivative Assets, Estimated Fair Value | 28.1 | 55.3
Derivative Liability, Notional Amount | 1,103.9 | 1,014.1
Derivative Liabilities, Estimated Fair Value | 18.2 | 17.9
Collateral Pledged |  |
Offsetting Derivative Liabilities [Abstract] |  |
Derivative, Collateral, Right to Reclaim Securities | 0.2 |
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] |  |
Derivative, Fair Value, Net | 7.8 |
Interest Rate Swap [Member] |  |
Derivative Asset [Abstract] |  |
Derivative Asset, Fair Value, Gross Asset | 26.3 | 52.0
Derivative Asset, Fair Value, Gross Liability | 0.0 | 0.0
Derivative Asset, Total | 26.3 | 52.0
Derivative, Collateral, Obligation to Return Securities | 0.0 | 0.0
Derivative, Collateral, Obligation to Return Cash | 8.0 | 17.2
Derivative Asset, Fair Value, Amount Offset Against Collateral, Total | 18.3 | 34.8
Offsetting Derivative Liabilities [Abstract] |  |
Derivative Liability, Fair Value, Gross Liability | 18.2 | 16.8
Derivative Liability, Fair Value, Gross Asset | 0.0 | 0.0
Derivative Liability, Total | 18.2 | 16.8
Derivative, Collateral, Right to Reclaim Securities | 0.0 | 0.0
Derivative, Collateral, Right to Reclaim Cash | 0.0 | 0.0
Derivative Liability, Fair Value, Amount Offset Against Collateral, Total | 18.2 | 16.8
Interest Rate Swap [Member] | Not Designated as Hedging Instrument |  |
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] |  |
Derivative Asset, Notional Amount | 913.9 | 799.7
Derivative Assets, Estimated Fair Value | 22.2 | 52.0
Derivative Liability, Notional Amount | 913.9 | 799.7
Derivative Liabilities, Estimated Fair Value | 18.1 | 16.6
Interest Rate Swap [Member] | Designated as Hedging Instrument |  |
Offsetting Derivative Liability, Securities Sold under Agreements to Repurchase, Securities Loaned [Abstract] |  |
Derivative Asset, Notional Amount | 700.0 | 0.0
Derivative Assets, Estimated Fair Value | 4.1 | 0.0
Derivative Liability, Notional Amount | 87.6 | 87.6
Derivative Liabilities, Estimated Fair Value | 0.1 | 0.2
Mortgage related derivatives |  |
Derivative Asset [Abstract] |  |
Derivative Asset, Fair Value, Gross Asset | 1.8 | 3.3
Derivative Asset, Fair Value, Gross Liability | 0.0 | 0.0
Derivative Asset, Total | 1.8 | 3.3
Derivative, Collateral, Obligation to Return Securities | 0.0 | 0.0
Derivative, Collateral, Obligation to Return Cash | 0.0 | 0.0
Derivative Asset, Fair Value, Amount Offset Against Collateral, Total | $ 1.8 | 3.3
Offsetting Derivative Liabilities [Abstract] |  |
Derivative Liability, Fair Value, Gross Liability |  | 1.1
Derivative Liability, Fair Value, Gross Asset |  | 0.0
Derivative Liability, Total |  | 1.1
Derivative, Collateral, Right to Reclaim Securities |  | 0.0
Derivative, Collateral, Right to Reclaim Cash |  | 0.0
Derivative Liability, Fair Value, Amount Offset Against Collateral, Total |  | $ 1.1

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