Basis of Presentation (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ASU 2016-13	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201613Member
Cumulative effect from adoption of CECL accounting standard		$ (1,960.5)	$ (1,973.5)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect from adoption of CECL accounting standard	$ (2,269.6)	(2,279.4)	$ (2,308.4)	$ (2,143.8)	$ (2,114.7)	$ (2,064.4)
Retained Earnings | Cumulative effect from adoption of CECL accounting standard (Note1)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect from adoption of CECL accounting standard		$ 1.0