Financial Instruments and Fair Value Measurements (Schedule of Carrying Amount and Fair Value of Long-term Debt) (Details) - USD ($) $ in Millions	Sep. 29, 2017	Dec. 30, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt, Current Maturities	$ 318.8	$ 271.8
Long-term Debt	5,592.5	5,965.8
Receivable Securitization
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Variable Rate Receivable Securitization	0.0	250.0
Variable Rate Receivable Securitization, Fair Value	0.0	250.0
Receivable securitization, Maturity Date of July 2020 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	200.0	0.0
Long-term Debt	200.0	0.0
4.00% Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Loans Payable	0.0	6.5
Loans Payable, Fair Value Disclosure	0.0	6.5
Secured Debt \| Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt, Current Maturities	0.0	20.0
Loans Payable	0.0	1,948.5
Long-term Debt	0.0	1,928.5
Loans Payable, Fair Value Disclosure	0.0	1,953.2
Secured Debt \| 4.00% Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt, Current Maturities	0.0	1.0
Long-term Debt	0.0	5.5
Secured Debt \| New Term Loan
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt, Current Maturities	18.6	0.0
Loans Payable	1,855.7	0.0
Long-term Debt	1,837.1	0.0
Loans Payable, Fair Value Disclosure	1,853.8	0.0
Secured Debt \| 2017 Revolving Credit Facility [Member] [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	0.0
Long-term Debt	0.0
Secured Debt \| 2015 Revolving Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value		100.0
Long-term Debt		100.0
Senior Notes \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	300.2	298.7
Senior Notes \| 5.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	853.3	850.3
Senior Notes \| 4.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	448.5	520.9
Unsecured Debt \| 3.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt, Current Maturities	300.0	0.0
Long-term Debt	0.0	300.0
Unsecured Debt \| 4.88% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	696.7	699.5
Long-term Debt	700.0	700.0
Unsecured Debt \| 5.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt	884.0	884.0
Unsecured Debt \| 4.75% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long-term Debt	526.5	600.0
Unsecured Debt \| 5.625% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	689.5	682.4
Long-term Debt	738.0	738.0
Unsecured Debt \| 5.50% Senior Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	625.4	615.7
Long-term Debt	692.1	695.0
Debentures \| 9.50% Debenture
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	11.5	12.0
Long-term Debt	10.4	10.4
Debentures \| 8.00% Debenture
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Long term debt, fair value	4.7	4.9
Long-term Debt	$ 4.4	$ 4.4

Variable Rate Receivable Securitization

No definition available.

Name:	mnk_VariableRateReceivableSecuritization
Namespace Prefix:	mnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Variable Rate Receivable Securitization, Fair Value

+ References

No definition available.

+ Details

Name:	mnk_VariableRateReceivableSecuritizationFairValue
Namespace Prefix:	mnk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Including the current and noncurrent portions, aggregate carrying value as of the balance sheet date of loans payable (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16)(a)(2))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_LoansPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of contractual obligation to pay money on demand or on fixed or determinable dates.

+ References

No definition available.

+ Details

Name:	us-gaap_LoansPayableFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant