Recent Accounting Pronouncements (Narrative) (Details) - USD ($) $ in Millions	Jan. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	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		$ 215.4	$ 210.2		$ 104.5	$ 105.7	$ 110.8		$ 112.6
Stockholders equity		(11,579.1)	(11,382.2)	$ (10,879.7)	(11,091.0)	(10,811.3)	(10,805.5)	$ (10,616.2)	(10,508.3)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders equity		$ (12,118.3)	$ (11,988.4)	$ (11,828.1)	(11,656.7)	$ (11,441.2)	$ (11,225.5)	$ (10,972.9)	$ (10,776.8)
Cumulative Effect Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 13.7				(2.2)
Stockholders equity					10.1
Cumulative Effect Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders equity	$ 10.1				$ 10.1