Fair Value Measurement (Assets and Liabilities Measured on a Recurring Basis) (Details) - Recurring Basis - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Level 1
Financial assets:
Marketable equity securities	$ 69.7	$ 65.8
Marketable debt securities	3.7	3.6
Contingent consideration receivable	0.0	0.0
Derivative instruments	0.0	0.0
Total assets	73.4	69.4
Financial liabilities:
Joint venture net written option	0.0
Derivative instruments	0.0	0.0
Contingent consideration payable	0.0	0.0
Total liabilities	0.0	0.0
Level 2
Financial assets:
Marketable equity securities	0.0	0.0
Marketable debt securities	13.0	11.9
Contingent consideration receivable	0.0	0.0
Derivative instruments	17.0	18.0
Total assets	30.0	29.9
Financial liabilities:
Joint venture net written option	0.0
Derivative instruments	8.8	8.3
Contingent consideration payable	0.0	0.0
Total liabilities	8.8	8.3
Level 3
Financial assets:
Marketable equity securities	0.0	0.0
Marketable debt securities	0.0	0.0
Contingent consideration receivable	8.3	15.6
Derivative instruments	0.0	0.0
Total assets	8.3	15.6
Financial liabilities:
Joint venture net written option	25.0
Derivative instruments	0.0	0.0
Contingent consideration payable	1,186.9	1,058.0
Total liabilities	1,211.9	1,058.0
Fair value
Financial assets:
Marketable equity securities	69.7	65.8
Marketable debt securities	16.7	15.5
Contingent consideration receivable	8.3	15.6
Derivative instruments	17.0	18.0
Total assets	111.7	114.9
Financial liabilities:
Joint venture net written option	25.0
Derivative instruments	8.8	8.3
Contingent consideration payable	1,186.9	1,058.0
Total liabilities	$ 1,220.7	$ 1,066.3