Fair Value Measurements - Additional Information (Details)			3 Months Ended																					5 Months Ended	6 Months Ended		12 Months Ended						44 Months Ended
		Mar. 27, 2017 USD ($)	Dec. 31, 2017 USD ($)		Sep. 30, 2017 USD ($)	[3]	Jul. 01, 2017 USD ($)	[4]	Apr. 01, 2017 USD ($)		Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)		Oct. 01, 2016 USD ($)		Jul. 02, 2016 USD ($)	[8]	Apr. 02, 2016 USD ($)		Dec. 31, 2015 USD ($)		Sep. 26, 2015 USD ($)	[11]	Apr. 30, 2014	Dec. 31, 2015 USD ($)	Dec. 27, 2014 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) reporting_unit	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 27, 2015 USD ($)	Dec. 31, 2017 USD ($)	Mar. 01, 2016 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percent of royalty revenues generated by specific agreement																								12.00%
Net sales	[1]																								$ 2,632,200,000				$ 4,946,200,000	$ 5,280,600,000		$ 4,227,100,000
Royalty stream discrete period																													20
Discount rate																															7.72%	7.83%
Discrete growth rate														2.00%						3.40%
Change in financial assets, gain (loss)			$ (700,000)	[2]	$ (2,600,000)		$ (38,700,000)		$ 17,100,000	[5]	$ (1,100,000,000)	$ (1,115,600,000)	[6]	$ (377,400,000)	[7]	$ (910,800,000)		$ (204,400,000)	[9]	$ (116,600,000)	[10]	$ 173,800,000			57,300,000	$ 46,900,000			$ (24,900,000)	(2,608,200,000)		$ 78,500,000
Discount rate on fair value asset, percent																															0.50%	0.50%
Fair value, assets, sensitivity analysis, effect of 0.5 percent increase in discount rate, decrease in fair value																				270,000,000					270,000,000						$ 270,000,000	$ 290,000,000
Fair value, assets, sensitivity analysis, effect of 0.5 percent decrease in discount rate, increase in fair value																				260,000,000					260,000,000						$ 260,000,000	$ 260,000,000
Discount Rate, royalty evaluation, percent																															5.00%	5.00%
Sensitivity analysis, effect of 5.0 percent increase in royalty rate, increase in fair value																				270,000,000					270,000,000						$ 270,000,000	$ 280,000,000
Sensitivity analysis, effect of 5.0 percent decrease in royalty rate, decrease in fair value																				280,000,000					280,000,000						280,000,000	280,000,000
Net proceeds from sale of business and other assets																									0				154,600,000	69,100,000		0
Gain (loss) on disposition of business									21,800,000
Royalty Pharma contingent milestone payments																																		$ 30,000,000
Guarantor maximum exposure			34,900,000																										34,900,000				$ 34,900,000
Gain (loss) on settlement of contingent consideration																													$ 17,400,000
Number of reporting units | reporting_unit																													6
Goodwill impairment charge												224,100,000		$ 737,900				130,500,000							0					1,092,500,000
Impairment of intangible assets, indefinite-lived									12,200,000																185,100,000				$ 12,700,000	849,500,000
Goodwill			4,175,400,000								4,049,400,000	4,049,400,000								5,152,700,000					5,152,700,000				4,175,400,000	4,049,400,000	5,152,700,000	4,721,200,000	4,175,400,000
Indefinite-lived intangible assets, gross			90,300,000								114,500,000	114,500,000								1,916,300,000					1,916,300,000				90,300,000	114,500,000	1,916,300,000		90,300,000
Impairment of intangible assets, definite-lived intangible																													19,700,000	665,600,000
Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Royalty Pharma contingent milestone payments			134,500,000								0	0								0					0				134,500,000	0	0		134,500,000
Change in fair value																													42,000,000
Guarantee on certain obligations			13,800,000																										13,800,000				13,800,000
Specialty Sciences
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain (loss) on disposition of business									$ 17,100,000
Goodwill impairment charge											199,600,000																			199,600,000
Goodwill			0								0	0								199,600,000					199,600,000				0	0	199,600,000	199,600,000	0
CHCI
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net sales																									833,000,000				1,491,000,000	1,652,200,000		704,600,000
Goodwill impairment charge																		$ 130,500,000												868,400,000
Impairment of intangible assets, indefinite-lived											30,500,000														185,100,000				1,100,000
Goodwill			$ 1,205,700,000								$ 1,070,800,000	$ 1,070,800,000								$ 1,983,200,000					1,983,200,000				1,205,700,000	1,070,800,000	$ 1,983,200,000	$ 1,530,200,000	1,205,700,000
Impairment of intangible assets, definite-lived intangible																													$ 0	$ 321,400,000
Royalty Pharma
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sale price of divestiture - cash plus non-cash		$ 2,850,000,000
Net proceeds from sale of business and other assets		2,200,000,000
Contingent proceeds from divestiture of business, milestone one, maximum		250,000,000
Contingent proceeds from divestiture of business, milestone two, maximum		$ 400,000,000
Expected volatility rate																													30.00%
Rate of return			8.07%
Royalty Pharma Contingent Milestone Payments [Member] | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Royalty Pharma contingent milestone payments			$ 134,500,000																										$ 134,500,000				$ 134,500,000
Goodwill | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																													7.50%
Long-term growth rates																													2.00%
Goodwill | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																													13.50%
Long-term growth rates																													3.00%
Tysabri | Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percent of royalty revenues generated by specific agreement																																	18.00%
Net sales																																	$ 2,000,000,000
Tysabri | Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Percent of royalty revenues generated by specific agreement																																	25.00%
Net sales																																	$ 2,000,000,000
Lumara
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																													13.50%
Discrete growth rate																													(4.10%)
Omega - Lifestyle
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																														9.30%
Discrete growth rate																														2.50%
Long-term growth rates																														2.00%
Omega-XLS
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																														9.50%
Discrete growth rate																														3.20%
Entocort - Branded Products
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																														13.00%
Discrete growth rate																														(31.70%)
Long-term growth rates																														(10.00%)
Entocort - AG Products
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																														10.50%
Discrete growth rate																														(30.40%)
Long-term growth rates																														(4.70%)
Herron Trade Names and Trademarks
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate																														10.80%
Discrete growth rate																														4.60%
Long-term growth rates																														2.50%
Forecast
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in financial assets, gain (loss)																											$ 345,200,000	$ 170,300,000
Royalty Pharma contingent milestone payments																											54,800,000	79,700,000
Assets, Fair Value Adjustment																											400,000,000	250,000,000
Net sales threshold for milestone payment																											$ 2,000,000,000	$ 1,900,000,000
Contingent consideration | Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Provision for new credit guarantees																									$ 0				$ 12,500,000	$ 0

[1] The net sales by geography is derived from the location of the entity that sells to a third party.

[2] (5) Includes unusual litigation charge reversal of $0.2 million.Year Ended December 31, 2016FirstQuarter (2) SecondQuarter (3) ThirdQuarter (4) FourthQuarter (5)Net sales$1,347.3 $1,340.5 $1,261.6 $1,331.2Gross profit$533.1 $546.5 $484.5 $487.7Change in financial assets$204.4 $910.8 $377.4 $1,115.6Net loss$(529.2) $(534.3) $(1,590.2) $(1,359.1)Loss per share(1): Basic$(3.70) $(3.73) $(11.10) $(9.48)Diluted$(3.70) $(3.73) $(11.10) $(9.48)Weighted average shares outstanding Basic143.2 143.2 143.3 143.4Diluted143.2 143.2 143.3 143.4

[3] Includes held-for-sale impairment charges of $3.3 million, and fixed asset impairment charges of $4.0 million.

[4] Includes intangible asset impairment charges of $18.5 million, changes in financial assets of $38.7 million, and loss on early debt extinguishment of $135.2 million.

[5] Includes IPR&D impairment charges of $12.2 million, gain on certain divestiture of $21.8 million, and restructuring charges of $38.7 million.

[6] Includes intangible asset impairment charges of $378.6 million, goodwill impairment charge of $224.1 million, and a reduction in held-for-sale impairment charges of $4.5 million.

[7] Includes intangible asset impairment charges of $866.6 million, goodwill impairment charge of $737.9 thousand, and held-for-sale impairment charges of $10.2 million.

[8] Includes held-for-sale impairment charges of $10.5 million and change in financial assets of $910.8 million.

[9] Includes an intangible asset impairment charges of $273.3 million, and a goodwill impairment charge of $130.5 million.

[10] Includes an intangible asset impairment charge of $185.1 million, Mylan defense-related fees of $71.3 million, an impairment charge on our India API held for sale assets of $29.0 million, restructuring charges of $24.7 million, and an investment impairment charge of $10.7 million.

[11] Includes Mylan defense-related fees of $15.6 million.