Recent Accounting Pronouncements Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings	$ 10,776.8	$ 9,685.1
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings				$ (0.5)
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income	(25.3)	0.0	$ 0.0
ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income	(25.3)
RETAINED EARNINGS
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income	25.3	$ 0.0	$ 0.0
RETAINED EARNINGS | Accounting Standards Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income	$ 25.3
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings				$ (4.0)