Loans (Components of Net Investment) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Receivables [Abstract]
Unearned income	$ (440.2)	$ (430.0)
Unamortized premiums / (discounts)	(550.4)	30.0
Accretable yield on PCI loans		(745.4)
Net unamortized deferred costs and (fees)	$ 49.7	$ 50.9