Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities	$ 844.0	$ 532.4
Net cash used in financing activities	$ (295.6)	(76.7)
Accounting Standards Update 2016-09, Excess Tax Benefit Component [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities		5.6
Net cash used in financing activities		$ (5.6)
Accounting Standards Update 2016-09, Excess Tax Benefit Component [Member] | Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment			$ 9.0