Debt Revolving Credit Agreement (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Jun. 17, 2016
Line of Credit Facility [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	$ 200.0
Current portion of deferred revenue	0.0
Proceeds from Lines of Credit	$ 75.0
Debt Instrument, Term	6 months
Proceeds from issuance of convertible debt, net of issuance costs	$ 389.0	$ 0.0
Line of Credit [Member]
Line of Credit Facility [Line Items]
Long-term Line of Credit			$ 200.0
Debt Issuance Costs, Line of Credit Arrangements, Gross			0.7
Line of Credit [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			10.0
Line of Credit Facility, Remaining Borrowing Capacity	$ 5.6
Foreign Currency Line of Credit [Member] | Letter of Credit [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 25.0
Maximum | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			2.75%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.45%
Minimum | Line of Credit [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			0.75%
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.25%