Allowance For Credit Losses - Off-Balance Sheet (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 5.6
Provision charged (credited) to income	0.6
Balance at end of period	20.7
Cumulative Effect, Period Of Adoption, Adjustment
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	14.5
Cumulative Effect, Period Of Adoption, Adjusted Balance
Off-Balance Sheet, Credit Loss, Liability [Roll Forward]
Balance at beginning of period	$ 20.1