Recent Accounting Pronouncements Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss	$ 190.7	$ 104.5	$ 112.6	$ 131.2
Stockholders' equity attributable to parent	11,688.3	11,091.0	10,508.3	10,216.2
RETAINED EARNINGS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent	$ 12,207.7	11,656.7	$ 10,776.8	9,685.1
Cumulative Effect Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		(2.2)
Stockholders' equity attributable to parent		(10.1)		(4.5)
Cumulative Effect Adjustment | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit loss		13.7
Cumulative Effect Adjustment | RETAINED EARNINGS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent		(10.1)		$ (4.5)
Cumulative Effect Adjustment | RETAINED EARNINGS | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stockholders' equity attributable to parent		$ (10.1)