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Investment Securities - Investments In Private Equity Funds Subject to Lock-Up Periods (Details) - Private equity funds $ in Millions	Mar. 31, 2021 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 121.5
1 – 3 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	6.8
3 – 5 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	27.0
5 – 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	74.5
Greater than 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 13.2

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