Fair Value Measurements - Financial Instruments at Fair Value (Details) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Assets:
Goodwill		$ 3,979.8		$ 4,175.4		$ 4,049.4
Indefinite-lived intangible assets, gross		49.3		90.3
Definite-lived intangible assets, net		2,858.9		3,290.5
Recurring | Level 1
Assets:
Investment securities		9.4		17.0
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		9.4		17.0
Liabilities:
Foreign currency forward contracts		0.0		0.0
Contingent consideration		0.0		0.0
Total liabilities		0.0		0.0
Recurring | Level 2
Assets:
Investment securities		0.0		0.0
Foreign currency forward contracts		3.8		6.3
Funds associated with Israeli severance liability		13.0		16.3
Royalty Pharma contingent milestone payments		0.0		0.0
Total assets		16.8		22.6
Liabilities:
Foreign currency forward contracts		9.2		3.8
Contingent consideration		0.0		0.0
Total liabilities		9.2		3.8
Recurring | 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		323.2		134.5
Total assets		323.2		134.5
Liabilities:
Foreign currency forward contracts		0.0		0.0
Contingent consideration		15.3		22.0
Total liabilities		15.3		22.0
Nonrecurring
Assets:
Indefinite-lived intangible assets, gross		46.9
Definite-lived intangible assets, net		72.0		31.2
Nonrecurring | Level 1
Assets:
Total assets		0.0		0.0
Goodwill		0.0		0.0
Indefinite-lived intangible assets		0.0		0.0
Definite-lived intangible assets		0.0		0.0
Nonrecurring | Level 2
Assets:
Total assets		0.0		0.0
Goodwill		0.0		0.0
Indefinite-lived intangible assets		0.0		0.0
Definite-lived intangible assets		0.0		0.0
Nonrecurring | Level 3
Assets:
Total assets		75.1		11.5
Goodwill		42.2	[1]	0.0
Indefinite-lived intangible assets		10.5	[2]	0.0
Definite-lived intangible assets	[3]	22.4		11.5
CHCA
Assets:
Goodwill		1,713.7	[4]	$ 1,847.4	[4]	$ 1,810.6
CHCA | Nonrecurring
Assets:
Goodwill		$ 178.9

[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] 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] 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. As of December 31, 2017, definite-lived intangible assets with a carrying amount of $31.2 million were written down to a fair value of $11.5 million.

[4] (1) We had accumulated impairments of $161.2 million and $24.5 million for the years ended December 31, 2018 and December 31, 2017, respectively.