Significant Clients - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 25, 2020 USD ($) Client	Sep. 27, 2019 USD ($) Client	Sep. 25, 2020 USD ($) Client	Sep. 27, 2019 USD ($) Client	Dec. 31, 2019 USD ($)
Segment Reporting Information [Line Items]
Accounts receivable, net	$ 74,907		$ 74,907		$ 88,772
Number of major client | Client	1	1	1	1
Number of other major client | Client	0	0	0	0
Customer Concentration Risk [Member] | Sales Revenue, Services, Net [Member]
Segment Reporting Information [Line Items]
Revenue, percent	100.00%	100.00%	100.00%	100.00%
IBM [Member]
Segment Reporting Information [Line Items]
Revenue	$ 18,600	$ 21,300	$ 57,400	$ 63,400
Services agreement expiration date	Nov. 27, 2020
Accounts receivable, net	$ 13,900		$ 13,900		$ 23,000
IBM [Member] | Customer Concentration Risk [Member] | Sales Revenue, Services, Net [Member]
Segment Reporting Information [Line Items]
Revenue, percent	21.00%	21.90%	21.70%	21.50%