Share-based Compensation Arrangement by Share-based Payment Award, Awards, Grants in Period, Fair Value

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Aggregate number of common shares reserved for future issuance.

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Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as current. Excludes other postretirement benefit plan.

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Amount of liability, recognized in statement of financial position, for defined benefit pension plan, classified as noncurrent. Excludes other postretirement benefit plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of discretionary contributions made by an employer to a defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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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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Amount of paid and unpaid cash dividends declared for award under share-based payment arrangement.

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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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Amount of cost to be recognized for option under share-based payment arrangement.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree.

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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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- Definition

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 number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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

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

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Purchase price of common stock expressed as a percentage of its fair value.

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Employee Benefit Plans and Stock-based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 25, 2020	Mar. 27, 2020	Sep. 27, 2019	Sep. 25, 2020	Sep. 27, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Realized Tax Benefits, Stock Option Exercised				$ 0	$ 0
Total stock-based compensation	$ 3,930,000		$ 4,096,000	13,737,000	8,719,000
Defined Benefit Plan, Benefit Obligation	5,700,000			5,700,000		$ 5,300,000
Liability, Defined Benefit Pension Plan, Current	100,000			100,000
Liability, Defined Benefit Pension Plan, Noncurrent	$ 5,600,000			$ 5,600,000
Discretionary contributions of plan				25.00%
Percent of employees' gross pay eligible for matching				4.00%
Maximum contribution amount per participant				$ 1,000
Contributions in period				243,000	$ 245,000
Dividend, Share-based Payment Arrangement, Cash				$ 0
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized				1,000,000
Common Stock, Capital Shares Reserved for Future Issuance	1,200,000			1,200,000
Discount Percentage On Purchase Of Stock				15.00%
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized				4,000,000
Common Stock, Capital Shares Reserved for Future Issuance	6,900,000			6,900,000
Grants in Period, Number of Shares				0
Performance-Based RSU Awards to Settle Incentive Bonus Payments [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Grants in Period				507,555	120,261
Total stock-based compensation				$ 3,200,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Grants in Period		67,910
Total stock-based compensation	$ 100,000			500,000
Nonvested Award, Option, Unrecognized Stock-based Compensation, Amount	200,000			200,000
PerformanceBased RSU Awards 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Grants in Period						85,000
Nonvested Award, Option, Unrecognized Stock-based Compensation, Amount	100,000			$ 100,000
Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				40,000
Market-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Award, Grants in Period		182,830
Total stock-based compensation	200,000		100,000	$ 500,000	$ 200,000
Nonvested Award, Option, Unrecognized Stock-based Compensation, Amount	1,400,000		$ 900,000	$ 1,400,000	$ 900,000
Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				0
Share-based Payment Award, Award Vesting Period		3 years
Share-based Payment Award, Awards, Grants in Period, Fair Value		$ 1,100,000
Market Based Award 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested Award, Option, Unrecognized Stock-based Compensation, Amount	600,000			$ 600,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested RSUs Award, Total Unrecognized Stock-based Compensation, Amount	$ 16,100,000			$ 16,100,000
Nonvested Award, Cost Not yet Recognized, Weighted-average Period for Recognition				1 year 9 months
TVN [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment for Pension and Other Postretirement Benefits				$ 0
Call Option [Member] \| Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of Common Stock to purchase shares				85.00%
Put Option [Member] \| Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of fair market value of Common Stock to purchase shares				15.00%