New Accounting Standards (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Tax expense (benefit)	$ 2.9	$ 17.0	$ 5.1	$ 23.9
Accounting Standards Update 2016-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit from share-based compensation, Operating activities			25.5
Tax expense (benefit)	(9.6)		(25.5)
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating leases, Future minimum payments due	71.8		71.8
Accounting Standards Update 2016-16 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New accounting pronouncement cumulative effect of change on equity	$ (4.1)		$ (4.1)