Employee Benefit Plans and Stock-based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 28, 2018	Jun. 29, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017	Dec. 31, 2017	Jan. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 0		$ 0	$ 0	$ 0
Total stock-based compensation	5,433,000		$ 3,720,000	14,202,000	11,107,000
Defined Benefit Plan, Benefit Obligation	5,100,000			5,100,000		$ 5,000,000
Liability, Defined Benefit Pension Plan, Current	100,000			100,000
Liability, Defined Benefit Pension Plan, Noncurrent	5,000,000			$ 5,000,000
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				259,000	$ 326,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 10,900,000			$ 10,900,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition				1 year 7 months 6 days
Dividends, Share-based Compensation, Cash				$ 0
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	4,500,000			4,500,000
Performance-based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				1,443,168
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				1,343,168
Total stock-based compensation	$ 2,600,000			$ 6,000,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	200,000			$ 200,000
Market-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		40,000				344,500
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period				0
Total stock-based compensation	$ 36,775			$ 200,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		18 months				3 years
Aggregate Grant Date Fair Value of Market-Based Restricted Stock Units				$ 1,300,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition				1 year 3 months 18 days
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				1,300,000
Common Stock, Capital Shares Reserved for Future Issuance	1,300,000			1,300,000
Discount Percentage On Purchase Of Stock				15.00%
Equity Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in Period, Number of Shares				0
TVN [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment for Pension and Other Postretirement Benefits				$ 0
Director Option Plans 2002 [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				400,000
Accounting Standards Update 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Modified Retrospective Cumulative Effect Adjustment to Retained Earnings							$ 69,000
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%