Debt (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016 USD ($) NotesConverted	Sep. 30, 2016 USD ($) NotesConverted
Senior Subordinated Convertible Notes [Member]
Debt Instrument [Line Items]
Stated interest rate percentage - debt instruments	3.75%	3.75%
Maturity date of debt		Jan. 15, 2034
First conversion date		Jan. 15, 2009
Number of notes converted | NotesConverted	7,670	7,670
Cash payments for debt conversions		$ 17.3
Deferred tax liability		0.9
Credit Facility Member 2012 [Member]
Line of Credit Facility [Line Items]
Unamortized Debt Issuance Expense	$ 0.9	0.9
Credit Facility Member 2016 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Description	five-year unsecured credit facility composed of a five year $2.5 billion revolving credit facility
Line of Credit Facility, Initiation Date	Sep. 23, 2016
Line of Credit Facility, Expiration Date	Sep. 23, 2021
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,500.0	$ 2,500.0
Debt covenant compliance	3.5	3.5