Commitments and Credit Risk (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Loan commitments	$ 254.4	$ 223.5
Capital committed to Small Business Investment Company fund, not contributed	2.3
Capital Addition Purchase Commitments
Other Commitments [Line Items]
Construction related contract commitment	65.1
Construction related contract commitment, not yet incurred	$ 61.3
Construction related contract commitment, term	2 years