Basis of Presentation - Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Convertible senior notes
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Debt instrument, interest rate, stated percentage	4.50%
Long-term debt	$ 80.3	$ 89.1
Senior Notes due 2022
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,525.0	1,479.8
Senior Notes due 2021
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	524.6	507.5
Senior Notes due 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	922.5	920.3
Senior Notes due 2018
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	271.8	271.0
Term loan facility
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,591.0	1,590.0
Senior Debentures due 2034
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	198.2	201.0
Euro private placement notes due 2020
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	14.6	13.9
Level 1 | Convertible senior notes
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	80.3	89.1
Level 1 | Senior Notes due 2022
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,525.0	1,479.8
Level 1 | Senior Notes due 2021
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	524.6	0.0
Level 1 | Senior Notes due 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	922.5	920.3
Level 1 | Senior Notes due 2018
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	271.8	0.0
Level 1 | Term loan facility
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	0.0
Level 1 | Senior Debentures due 2034
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	198.2	0.0
Level 1 | Euro private placement notes due 2020
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	0.0
Level 2 | Convertible senior notes
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	0.0
Level 2 | Senior Notes due 2022
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	0.0
Level 2 | Senior Notes due 2021
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	507.5
Level 2 | Senior Notes due 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	0.0
Level 2 | Senior Notes due 2018
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	271.0
Level 2 | Term loan facility
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,591.0	1,590.0
Level 2 | Senior Debentures due 2034
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	0.0	201.0
Level 2 | Euro private placement notes due 2020
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	14.6	13.9
Cash equivalents
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	136.7	83.2
Cash equivalents | Level 1
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	30.1	9.1
Cash equivalents | Level 2
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	106.6	74.1
Carrying Value | Convertible senior notes
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	45.7	46.8
Carrying Value | Senior Notes due 2022
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,578.4	1,577.0
Carrying Value | Senior Notes due 2021
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	547.8	536.6
Carrying Value | Senior Notes due 2019
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	900.3	900.4
Carrying Value | Senior Notes due 2018
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	267.7	268.2
Carrying Value | Term loan facility
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	1,535.7	1,540.3
Carrying Value | Senior Debentures due 2034
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	199.9	199.0
Carrying Value | Euro private placement notes due 2020
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Long-term debt	14.6	14.5
Carrying Value | Cash equivalents
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	$ 136.7	$ 83.2