Business Combination, Equity Conversion, Post-Combination Expense

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- Definition

Defined Contribution Plan, Employer Matching Contribution, Amount

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- Definition

Employee Service Share-based Compensation, Tax Benefit from U.S. Tax Reform Measurement

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- Definition

Performance Shares Award, Performance Period

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Performance Shares, Percentage of Ordinary Shares Awarded

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- Definition

Share-Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Granted in Period, Total Fair Value

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
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- Definition

Amount of deferred tax expense from write-off of the deferred tax asset related to deductible stock options at exercise.

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-Name Accounting Standards Codification
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- Definition

Percentage employer matches of the employee's percentage contribution matched.

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Maximum amount the employee may contribute to a defined contribution plan.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested share-based awards, other than options, awarded to employees as compensation.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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- Definition

Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Discount rate from fair value on purchase date that participants pay for shares.

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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- 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.

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- Definition

Number of additional shares authorized for issuance under an established share-based compensation plan.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

Amount by which current fair value of underlying stock exceeds exercise price of fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Share Plans (Narrative) (Details) - USD ($)	3 Months Ended	12 Months Ended
Share Plans (Narrative) (Details) - USD ($)	Dec. 30, 2016	Dec. 29, 2017	Sep. 30, 2016	Sep. 25, 2015	Sep. 26, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation cost	$ 10,600,000	$ 58,500,000	$ 41,400,000	$ 115,000,000
Tax benefit from share-based compensation cost	3,600,000	11,000,000	13,100,000	41,300,000
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options		16,000,000
Employee Service Share-based Compensation, Tax Benefit from U.S. Tax Reform Measurement		5,000,000
Intrinsic value of options vested	300,000	1,400,000	15,300,000	89,500,000
Tax benefit from stock options exercised	$ 100,000	$ 500,000	$ 5,700,000	$ 33,100,000
Performance period		3 years
Share Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		4 years
Expiration period		10 years
Unrecognized compensation cost, share options		$ 37,700,000
Weighted-average period to recognize unrecognized compensation cost, share options		2 years 6 months
Restricted Share Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value, granted restricted share units	$ 69.08	$ 50.74	$ 70.10	$ 105.68
Vesting period		4 years
Weighted-average period to recognize unrecognized compensation cost, share options		2 years 5 months
Fair value of restricted share units granted in period		$ 50,700,000
Fair value of restricted share units vested in period		69,100,000
Unrecognized compensation cost, restricted share units		$ 42,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employer matching contribution, percent of match				25.00%	15.00%
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date		15.00%
ESPP employer match - maximum employee contribution				$ 25,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value, granted restricted share units		$ 51.73	$ 83.00	$ 125.84
Unrecognized compensation cost		$ 18,500,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value, granted restricted share units		$ 70.88
Fair value of restricted share units vested in period		$ 400,000
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under 2013 Plan		5,700,000.0
2015 Mallinckrodt Pharmaceuticals Stock and Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized under 2013 Plan		17,800,000.0
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized		12,100,000.0
Questcor Pharmaceuticals, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Post combination expense				$ 90,400,000
Selling, general and administrative \| Questcor Pharmaceuticals, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Post combination expense				80,600,000
Restructuring \| Questcor Pharmaceuticals, Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Post combination expense				$ 9,800,000
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of ordinary shares to be awarded		0.00%
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of ordinary shares to be awarded		200.00%
New ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount		$ 25,000