Commitments and Credit Risk (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Other Commitments [Line Items]
Loan commitments	$ 278.7	$ 254.4
Capital committed to Small Business Investment Company fund, not contributed	1.7
Capital Addition Purchase Commitments
Other Commitments [Line Items]
Construction related contract commitment	65.1
Construction related contract commitment, not yet incurred	$ 44.7
Construction related contract commitment, term	2 years