Other Real Estate Owned (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Real Estate Acquired Through Foreclosure [Roll Forward]
Beginning balance	$ 2.0	$ 6.5	$ 2.5	$ 8.5
Additions	0.4	2.0	0.7	3.2
Valuation adjustments	0.0	(0.1)	0.0	(0.1)
Dispositions	(0.1)	(2.7)	(0.9)	(5.9)
Ending balance	2.3	$ 5.7	2.3	$ 5.7
Carrying values of foreclosed residential real estate properties	0.5		0.5		$ 0.0
Consumer mortgage loans collateralized by residential real estate property in the process of foreclosure	$ 0.6		$ 0.6		$ 0.2