Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details) - Private equity security $ in Millions	Jun. 30, 2018 USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 71.1
1-3 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	9.0
3-5 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	5.8
5-10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	42.7
Greater than 10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 13.6