Discontinued operations (Details) - USD ($) $ in Millions	3 Months Ended
	Apr. 01, 2017	Apr. 02, 2016	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash and cash equivalents	$ 3,077.8	$ 588.9	$ 622.3	$ 417.8
Net sales	1,194.0	1,347.3
Income (Loss) from Continuing Operations before Income Taxes, Domestic	95.8	(490.1)
Income tax expense	24.2	$ 39.1
Accounts receivable, net of allowance for doubtful accounts of $6.0 million and $6.3 million, respectively	1,050.2		1,176.0
Inventories	800.2		795.0
Prepaid expenses and other current assets	185.2		212.0
Property, plant and equipment, net	875.3		870.1
Tysabri® royalty stream	0.0		2,350.0
Other intangible assets, net	3,341.4		3,396.8
Other non-current assets	394.9		211.9
Accounts payable	$ 476.3		$ 471.7