The number of shares purchased by employees under the investment share purchase program.

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Share based compensation arrangement by share based payment award, fair value assumptions, estimated forfeiture rate.

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Share based compensation arrangement by share based payment award participants payment description.

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Employee tenure requirement to participate in plan.

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Stock repurchase program, cumulative number of shares repurchased.

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Stock repurchase program, cumulative shares repurchased, value.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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

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The number of grants made 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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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

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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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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No definition available.

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- Definition

Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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- Definition

Gross number of share options (or share units) granted during the period.

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No definition available.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Number of options outstanding, including both vested and non-vested options.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Fair value of options vested. Excludes equity instruments other than options, for example, but not limited to, share units, stock appreciation rights, restricted stock.

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Number of options vested.

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No definition available.

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Weighted average grant-date fair value of options vested.

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Common Stock and Share-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Apr. 30, 2018	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, contractual term		5 years 11 months 4 days
Other than options granted in period		42,530
Stock option outstanding		241,847	315,678
Options granted in period - weighted average fair value		$ 153.31	$ 131.91	$ 92.89
Weighted average fair value of stock awards		$ 350.96
Expected dividends		0.00%	0.00%	0.00%
Estimated forfeiture rate for equity awards that do not vest on January 1st		13.00%
Total fair value of options vested in period		$ 4,800	$ 2,500	$ 3,200
Aggregate intrinsic value of stock options exercised in period		45,900	$ 20,900	$ 19,200
Unrecognized compensation costs		$ 28,600
Unrecognized compensation costs, weighted average period		2 years
Option vested, number of shares		45,860	33,205	20,678
Option vested, weighted average fair value		$ 214.23	$ 188.63	$ 156.50
Repurchase of shares		13,797,037	13,797,037	13,797,037	13,447,346
Repurchased of value		$ 840,664	$ 840,664	$ 840,664	$ 752,352
President and Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period	9,959
Options granted in period - weighted average fair value	$ 100.50
Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option outstanding		14,962
Performance-Based Awards \| Board of Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option outstanding		24,699
Non-Employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period		4,410	4,779	5,080
Non-Employee Director \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, contractual term		10 years
Employee Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period		21,992	26,507	27,490
Employee Stock Compensation Plan \| Investment Share Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		5 years
Share based compensation arrangement by share based payment award participants payment description		Participants may pay for these shares either up front or through payroll deductions over an eleven-month period during the year of purchase.
Shares employees elected to purchase		9,127	7,901	9,214
Employee Stock Compensation Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
Employee Stock Compensation Plan \| Minimum \| Investment Share Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requirement tenure of employee for investment share program, purchase shares at discount		1 year
Discount from current market value		0.00%
Employee Stock Compensation Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		5 years
Stock options, contractual term		10 years
Employee Stock Compensation Plan \| Maximum \| Investment Share Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from current market value		40.00%
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted in period		33,403	22,509	83,561
Restricted Stock Awards \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted in period	64,325
Weighted average fair value of stock awards	$ 229.30
Restricted Stock Awards \| Performance-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted in period		2,696
Restricted Stock Awards \| Service-Based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted in period		30,707
Restricted Stock Awards \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		1 year
Restricted Stock Awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		5 years
Common Class A \| Non-Employee Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance		600,000
Shares available for grant		100,000
Common Class A \| Employee Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance		6,700,000
Shares available for grant		1,000,000.0