Schedule of Allowance For Credit Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 246.6	$ 240.4
Charge-offs	(12.6)	(7.5)
Recoveries	2.0	2.4
Net loan charge-offs	(10.6)	(5.1)
Provision for credit losses	33.5	5.6
Balance at end of period	341.7	240.9
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	217.9	209.5
Charge-offs	(9.7)	(6.4)
Recoveries	1.4	1.4
Net loan charge-offs	(8.3)	(5.0)
Provision for credit losses	19.5	4.5
Balance at end of period	211.8	209.0
Retail
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	28.7	30.9
Charge-offs	(2.9)	(1.1)
Recoveries	0.6	1.0
Net loan charge-offs	(2.3)	(0.1)
Provision for credit losses	14.0	1.1
Balance at end of period	129.9	$ 31.9
Cumulative Effect, Period Of Adoption, Adjustment
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	72.2
Cumulative Effect, Period Of Adoption, Adjustment | Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	(17.3)
Cumulative Effect, Period Of Adoption, Adjustment | Retail
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	$ 89.5