Fair Value Measurements - Financial Instruments at Fair Value (Details) - USD ($) $ in Millions	Mar. 30, 2019	Dec. 31, 2018
Measured at fair value on a non-recurring basis:
Goodwill carrying amount	$ 3,966.2	$ 3,979.8
Indefinite-lived intangible assets carrying value	32.8	49.3
Definite-lived intangible assets carrying value	2,757.9	2,858.9
Measured at fair value on a recurring basis | Level 1
Assets:
Investment securities	3.7	9.4
Foreign currency forward contracts	0.0	0.0
Funds associated with Israeli severance liability	0.0	0.0
Royalty Pharma contingent milestone payments	0.0	0.0
Total assets	3.7	9.4
Liabilities:
Foreign currency forward contracts	0.0	0.0
Contingent consideration	0.0	0.0
Total liabilities	0.0	0.0
Measured at fair value on a recurring basis | Level 2
Assets:
Investment securities	0.0	0.0
Foreign currency forward contracts	3.2	3.8
Funds associated with Israeli severance liability	13.4	13.0
Royalty Pharma contingent milestone payments	0.0	0.0
Total assets	16.6	16.8
Liabilities:
Foreign currency forward contracts	5.8	9.2
Contingent consideration	0.0	0.0
Total liabilities	5.8	9.2
Measured at fair value on a recurring basis | Level 3
Assets:
Investment securities	0.0	0.0
Foreign currency forward contracts	0.0	0.0
Funds associated with Israeli severance liability	0.0	0.0
Royalty Pharma contingent milestone payments	83.6	323.2
Total assets	83.6	323.2
Liabilities:
Foreign currency forward contracts	0.0	0.0
Contingent consideration	12.4	15.3
Total liabilities	12.4	15.3
Measured at fair value on a non-recurring basis
Measured at fair value on a non-recurring basis:
Indefinite-lived intangible assets carrying value		46.9
Definite-lived intangible assets carrying value		72.0
Measured at fair value on a non-recurring basis | Level 1
Assets:
Total assets	0.0	0.0
Measured at fair value on a non-recurring basis:
Goodwill	0.0	0.0
Indefinite-lived intangible assets	0.0	0.0
Definite-lived intangible assets	0.0	0.0
Measured at fair value on a non-recurring basis | Level 2
Assets:
Total assets	0.0	0.0
Measured at fair value on a non-recurring basis:
Goodwill	0.0	0.0
Indefinite-lived intangible assets	0.0	0.0
Definite-lived intangible assets	0.0	0.0
Measured at fair value on a non-recurring basis | Level 3
Assets:
Total assets	0.0	75.1
Measured at fair value on a non-recurring basis:
Goodwill	0.0	42.2	[1]
Indefinite-lived intangible assets	0.0	10.5	[2]
Definite-lived intangible assets	0.0	22.4	[3]
CSCA
Measured at fair value on a non-recurring basis:
Goodwill carrying amount	$ 1,714.9	1,713.7
CSCA | Measured at fair value on a non-recurring basis
Measured at fair value on a non-recurring basis:
Goodwill carrying amount		$ 178.9

[1] (1)As of December 31, 2018, goodwill with a carrying amount of $178.9 million was written down to a fair value of $42.2 million.

[2] (2)As of December 31, 2018, indefinite-lived intangible assets with a carrying amount of $46.9 million were written down to a fair value of $10.5 million.

[3] (3) As of December 31, 2018, definite-lived intangible assets with a carrying amount of $72.0 million were written down to a fair value of $22.4 million.