Investments Low Income Housing Tax Credits (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Investments, All Other Investments [Abstract]
Low Income Housing Tax Credits	$ 10.4	$ 10.4	$ 31.1	$ 31.3
Amortization of Low Income Housing Investments	(7.1)	(5.8)	(21.1)	(17.4)
Tax Benefits from Low Income Housing Investments	$ 3.3	$ 4.6	$ 10.0	$ 13.9