Investing Activities Investing Activities - Limited Partnerships and Other Investments (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Limited partnerships and other investments	$ 13.4	$ 12.5
Private equity funds
Schedule of Equity Method Investments [Line Items]
Equity method investments	8.8	8.4
Mezzanine funds
Schedule of Equity Method Investments [Line Items]
Equity method investments	0.2	0.0
Direct equity investments
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 4.4	$ 4.1