Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2020	Mar. 31, 2020	Jan. 01, 2020	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Allowance for credit loss	$ 104.5	$ 210.2	$ 147.2		$ 110.8	$ 114.5	$ 112.6
Stockholders' equity	11,091.0	$ 11,382.2	$ 10,879.7		$ 10,805.5	$ 10,616.2	$ 10,508.3
Cumulative Effect Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	(2.2)			$ 13.7
Stockholders' equity	$ (10.1)