Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended		18 Months Ended
	Mar. 30, 2015	Jul. 02, 2016	Jun. 27, 2015	Jul. 02, 2016	Jun. 27, 2015	Jul. 02, 2016	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Tysabri® royalty stream - change in fair value		$ 910.8	$ 69.2	$ 1,115.3	$ (31.5)
Non-current deferred income taxes		1,107.6		1,107.6		$ 1,107.6		$ 1,372.7
Net loss		(534.3)	(22.2)	(1,063.5)	(44.5)
Foreign currency translation adjustments		(107.6)	118.6	43.9	90.8
Adjustments | Tax Basis Intangible Assets Misstatement
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Non-current deferred income taxes							$ (236.3)
Adjustments | Tysabri Royalty Stream Fair Value Option Adjustments and Other Misstatements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss		(728.6)	$ 78.6	923.2	(6.1)
Foreign currency translation adjustments		$ (1.4)		$ (0.9)	$ 0.1
Cumulative effect on retained earnings						$ (41.7)
Omega
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Acquisition date	Mar. 30, 2015