Income Taxes - Textual (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Income Tax Contingency [Line Items]
Provision for income tax expense	$ 39.7	$ 30.3
Net Deferred Tax Assets, Total	145.0
Deferred Tax Assets, Valuation Allowance	27.6
Gross Operating Loss Carryforwards	183.0
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	15.5
Gross Unrecognized Tax Benefits	3.0		$ 2.9
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	3.0		$ 2.9
Federal
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net Operating Loss Carryforwards	64.1
Tax Credit Carryforward, Amount	15.0
Minimum [Member]
Income Tax Contingency [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	0.5
Maximum [Member]
Income Tax Contingency [Line Items]
Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit	$ 2.9