Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details) - Private equity security $ in Millions	Mar. 31, 2020 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 98.5
1-3 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	4.7
3-5 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	39.3
5-10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	43.3
Greater than 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 11.2