Other Real Estate Owned (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Repossessed Assets [Abstract]
Real Estate Acquired Through Foreclosure, Valuation Adjustments	$ 0.9	$ 0.1
Real Estate Acquired Through Foreclosure [Roll Forward]
Balance at beginning of year	14.4	10.1	$ 10.0
Acquisitions	2.4	0.6	1.2
Additions	14.1	12.1	5.4
Valuation adjustments	(0.9)	(0.1)	(0.4)
Dispositions	(21.8)	(8.3)	(6.1)
Balance at end of year	8.5	14.4	10.1
Real Estate Acquired Through Foreclosure, Improvements	0.3		0.0
Write-downs of OREO	$ (0.9)	$ (0.1)	$ (0.4)