Investments in Qualified Affordable Housing Projects, Federal Historic Projects and New Market Tax Credits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Remaining unfunded equity contributions	$ 143.8		$ 131.3
Qualified Affordable Housing Projects
Schedule of Equity Method Investments [Line Items]
Amortization expense	5.3	$ 2.5
Tax credits and other benefits	6.6	$ 3.0
Remaining investment amount	203.4		195.8
Federal Historical Projects and Ohio Historical Preservation Projects
Schedule of Equity Method Investments [Line Items]
Remaining investment amount	46.0		$ 43.6
Federal Historical Projects
Schedule of Equity Method Investments [Line Items]
Amortization expense	0.2
Tax credits and other benefits	0.3
Ohio Historical Preservation Projects
Schedule of Equity Method Investments [Line Items]
Tax credits and other benefits	$ 0.4