Investment Securities (Investments In Private Equity Funds Subject to Lock-Up Periods) (Details) - Private equity funds $ in Millions	Sep. 30, 2017 USD ($)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 81.1
1-3 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	4.0
3-5 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	18.2
5-10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	33.5
Greater than 10 years
Schedule of Trading Securities and Other Trading Assets [Line Items]
Other long-term investments	$ 25.4