Summary of Significant Accounting Policies - Condensed Consolidated Balance Sheet (Details) $ / shares in Units, $ in Millions	Jul. 02, 2016 USD ($) $ / shares shares	Jul. 02, 2016 € / shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2015 € / shares	Jun. 27, 2015 USD ($)	Dec. 27, 2014 USD ($)
Assets
Cash and cash equivalents	$ 641.8		$ 417.8		$ 785.6	$ 3,596.1
Accounts receivable, net of allowance for doubtful accounts of $5.4 million, and $4.5 million, respectively	1,194.1		1,189.0
Inventories	894.6		898.7
Prepaid expenses and other current assets	297.3		286.1
Total current assets	3,027.8		2,791.6
Property, plant and equipment, net	888.6		886.2
Tysabri® royalty stream - at fair value	4,020.0		5,310.0
Goodwill and other indefinite-lived intangible assets	6,425.8		7,069.0
Other intangible assets, net	3,607.6		2,973.1
Non-current deferred income taxes	109.3		71.4
Other non-current assets	212.1		248.3
Total non-current assets	15,263.4		16,558.0
Total assets	18,291.2		19,349.6		19,349.6
Allowance for doubtful accounts	5.4		4.5
Liabilities and Shareholders’ Equity
Accounts payable	509.1		555.8
Payroll and related taxes	98.4		125.3
Accrued customer programs	353.0		396.0
Accrued liabilities	295.7		351.9
Accrued income taxes	45.9		62.7
Current indebtedness	758.1		1,060.5
Total current liabilities	2,060.2		2,552.2
Long-term debt, less current portion	5,652.5		4,971.6
Non-current deferred income taxes	1,107.6		1,372.7
Other non-current liabilities	422.5		346.3
Total non-current liabilities	7,182.6		6,690.6
Total liabilities	9,242.8		9,242.8
Preferred shares, $0.0001 par value, 10 million shares authorized	0.0		0.0
Ordinary shares, €0.001 par value, 10 billion shares authorized	8,144.0		8,142.6
Accumulated other comprehensive income	30.7		(15.3)
Retained earnings	874.3		1,980.1
Total controlling interest	9,049.0		10,107.4
Noncontrolling interest	(0.6)		(0.6)
Total shareholders’ equity	9,048.4		10,106.8
Total liabilities and shareholders' equity	$ 18,291.2		$ 19,349.6
Preferred shares, par value (in dollars per share) | $ / shares	$ 0.0001		$ 0.0001
Preferred shares, authorized (in shares) | shares	10,000,000		10,000,000
Ordinary shares, par value (in dollars per share) | € / shares		€ 0.001		€ 0.001
Ordinary shares, authorized (in shares) | shares	10,000,000,000		10,000,000,000
Previously Reported
Assets
Cash and cash equivalents	$ 641.8		$ 417.8		785.6	3,596.1
Accounts receivable, net of allowance for doubtful accounts of $5.4 million, and $4.5 million, respectively	1,199.1		1,193.1
Inventories	894.6		844.4
Prepaid expenses and other current assets	297.3		289.1
Total current assets	3,032.8		2,744.4
Property, plant and equipment, net	888.6		886.2
Tysabri® royalty stream - at fair value	0.0		0.0
Goodwill and other indefinite-lived intangible assets	6,627.1		7,281.2
Other intangible assets, net	8,679.3		8,190.5
Non-current deferred income taxes	100.6		54.6
Other non-current assets	205.2		237.0
Total non-current assets	16,500.8		16,649.5
Total assets	19,533.6		19,393.9
Allowance for doubtful accounts	5.4		4.5
Liabilities and Shareholders’ Equity
Accounts payable	514.1		554.9
Payroll and related taxes	98.4		125.3
Accrued customer programs	354.2		398.0
Accrued liabilities	295.7		308.4
Accrued income taxes	72.5		85.2
Current indebtedness	758.1		1,018.3
Total current liabilities	2,093.0		2,490.1
Long-term debt, less current portion	5,652.5		4,971.6
Non-current deferred income taxes	1,473.7		1,563.7
Other non-current liabilities	414.7		332.4
Total non-current liabilities	7,540.9		6,867.7
Total liabilities	9,633.9		9,357.8
Preferred shares, $0.0001 par value, 10 million shares authorized			0.0
Ordinary shares, €0.001 par value, 10 billion shares authorized	8,144.0		8,144.6
Accumulated other comprehensive income	31.3		(15.5)
Retained earnings	1,725.0		1,907.6
Total controlling interest	9,900.3		10,036.7
Noncontrolling interest	(0.6)		(0.6)
Total shareholders’ equity	9,899.7		10,036.1
Total liabilities and shareholders' equity	$ 19,533.6		$ 19,393.9
Preferred shares, par value (in dollars per share) | $ / shares			$ 0.0001
Preferred shares, authorized (in shares) | shares			10,000,000
Ordinary shares, par value (in dollars per share) | € / shares		€ 0.001		€ 0.001
Ordinary shares, authorized (in shares) | shares	10,000,000,000		10,000,000,000
Adjustments | Tysabri®
Assets
Cash and cash equivalents	$ 0.0		$ 0.0		0.0	0.0
Accounts receivable, net of allowance for doubtful accounts of $5.4 million, and $4.5 million, respectively	0.0		0.0
Inventories	0.0		0.0
Prepaid expenses and other current assets	0.0		0.0
Total current assets	0.0		0.0
Property, plant and equipment, net	0.0		0.0
Tysabri® royalty stream - at fair value	4,020.0		5,310.0
Goodwill and other indefinite-lived intangible assets	0.0		0.0
Other intangible assets, net	(5,067.2)		(5,212.2)
Non-current deferred income taxes	0.0		0.0
Other non-current assets	0.0		0.0
Total non-current assets	(1,047.2)		97.8
Total assets	(1,047.2)		97.8
Allowance for doubtful accounts	0.0		0.0
Liabilities and Shareholders’ Equity
Accounts payable	0.0		0.0
Payroll and related taxes	0.0		0.0
Accrued customer programs	0.0		0.0
Accrued liabilities	0.0		0.0
Accrued income taxes	0.0		0.0
Current indebtedness	0.0		0.0
Total current liabilities	0.0		0.0
Long-term debt, less current portion	0.0		0.0
Non-current deferred income taxes	(130.9)		12.2
Other non-current liabilities	0.0		0.0
Total non-current liabilities	(130.9)		12.2
Total liabilities	(130.9)		12.2
Preferred shares, $0.0001 par value, 10 million shares authorized			0.0
Ordinary shares, €0.001 par value, 10 billion shares authorized	0.0		0.0
Accumulated other comprehensive income	0.0		0.0
Retained earnings	(916.3)		85.6
Total controlling interest	(916.3)		85.6
Noncontrolling interest	0.0		0.0
Total shareholders’ equity	(916.3)		85.6
Total liabilities and shareholders' equity	(1,047.2)		97.8
Adjustments | Other
Assets
Cash and cash equivalents	0.0		0.0		$ 0.0	$ 0.0
Accounts receivable, net of allowance for doubtful accounts of $5.4 million, and $4.5 million, respectively	(5.0)		(4.1)
Inventories	0.0		54.3
Prepaid expenses and other current assets	0.0		(3.0)
Total current assets	(5.0)		47.2
Property, plant and equipment, net	0.0		0.0
Tysabri® royalty stream - at fair value	0.0		0.0
Goodwill and other indefinite-lived intangible assets	(201.3)		(212.2)
Other intangible assets, net	(4.5)		(5.2)
Non-current deferred income taxes	8.7		16.8
Other non-current assets	6.9		11.3
Total non-current assets	(190.2)		(189.3)
Total assets	(195.2)		(142.1)
Allowance for doubtful accounts	0.0		0.0
Liabilities and Shareholders’ Equity
Accounts payable	(5.0)		0.9
Payroll and related taxes	0.0		0.0
Accrued customer programs	(1.2)		(2.0)
Accrued liabilities	0.0		43.5
Accrued income taxes	(26.6)		(22.5)
Current indebtedness	0.0		42.2
Total current liabilities	(32.8)		62.1
Long-term debt, less current portion	0.0		0.0
Non-current deferred income taxes	(235.2)		(203.2)
Other non-current liabilities	7.8		13.9
Total non-current liabilities	(227.4)		(189.3)
Total liabilities	(260.2)		(127.2)
Preferred shares, $0.0001 par value, 10 million shares authorized			0.0
Ordinary shares, €0.001 par value, 10 billion shares authorized	0.0		(2.0)
Accumulated other comprehensive income	(0.6)		0.2
Retained earnings	65.6		(13.1)
Total controlling interest	65.0		(14.9)
Noncontrolling interest	0.0		0.0
Total shareholders’ equity	65.0		(14.9)
Total liabilities and shareholders' equity	(195.2)		(142.1)
Adjustments | BCH Deferred Tax Matters Misstatement
Assets
Goodwill and other indefinite-lived intangible assets	229.0		223.3
Non-current deferred income taxes	278.4		272.2
Liabilities and Shareholders’ Equity
Accrued income taxes	(10.9)
Non-current deferred income taxes	33.7		65.4
Adjustments | BCH Belgium Distribution Contracts Misstatement
Assets
Goodwill and other indefinite-lived intangible assets	(5.4)		10.2
Liabilities and Shareholders’ Equity
Accrued income taxes	(6.1)
Non-current deferred income taxes	0.7		$ 8.7
Adjustments | Adjustments to Income Taxes Accounted For Under ASC 740
Liabilities and Shareholders’ Equity
Accrued income taxes	$ (8.1)