Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details) - Private equity security $ in Millions	Mar. 31, 2019 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 97.6
1-3 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	7.0
3-5 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	0.0
5-10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	67.9
Greater than 10 years
Debt and Equity Securities, FV-NI [Line Items]
Fair Value	$ 22.7