Derivative Financial Instruments - Cash Flow Hedges (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Mar. 31, 2021
Derivative [Line Items]
Unrealized gains on terminated cash flow hedges remaining in AOCI, before tax	$ 116.0
Changes in fair value on bank cash flow hedges, net of reclassification adjustments in bank net income	$ 83.0
Remaining term over which unrealized gains will be reclassified into earnings	3 years
Interest rate swaps \| Derivatives designated as hedging instruments
Derivative [Line Items]
Notional balances		$ 5,000.0
Net asset fair value		$ 228.0

Fair value of the assets less the liabilities of a derivative or group of derivatives.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
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Estimated period for the anticipated transfer of gain (loss), net, from accumulated other comprehensive income into earnings, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=124509347&loc=d3e637-108580

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Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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