Business Acquisitions - Summary of the fair values of assets acquired and liabilities assumed (Details) $ in Thousands	12 Months Ended
	Dec. 28, 2019 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items]
Cash	$ 6,969
Billed and unbilled receivables, net	62,587
Right-of-use assets	6,131
Property and equipment	18,309
Prepaid expenses	3,609
Other assets	2,365
Total Assets	230,001
Liabilities	(32,071)
Deferred tax liabilities	(31,105)
Net assets acquired	166,825
Consideration paid (Cash, Notes and/or stock)	368,875
Contingent earn-out liability (Cash and stock)	1,004
Total Consideration	369,879
Excess consideration over the amounts assigned to the net assets acquired (Goodwill)	203,054
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	81,675
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	5,599
Customer backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	8,999
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	32,944
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	814
Quantum Spatial, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Cash	6,894
Billed and unbilled receivables, net	42,523
Right-of-use assets	6,131
Property and equipment	16,146
Prepaid expenses	2,612
Other assets	1,317
Total Assets	191,689
Liabilities	(23,698)
Deferred tax liabilities	(27,476)
Net assets acquired	140,515
Consideration paid (Cash, Notes and/or stock)	318,428
Contingent earn-out liability (Cash and stock)	0
Total Consideration	318,428
Excess consideration over the amounts assigned to the net assets acquired (Goodwill)	177,913
Quantum Spatial, Inc. | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	71,252
Quantum Spatial, Inc. | Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	4,234
Quantum Spatial, Inc. | Customer backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	7,636
Quantum Spatial, Inc. | Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	32,944
Quantum Spatial, Inc. | Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	0
Other Business Acquisitions
Acquired Finite-Lived Intangible Assets [Line Items]
Cash	75
Billed and unbilled receivables, net	20,064
Right-of-use assets	0
Property and equipment	2,163
Prepaid expenses	997
Other assets	1,048
Total Assets	38,312
Liabilities	(8,373)
Deferred tax liabilities	(3,629)
Net assets acquired	26,310
Consideration paid (Cash, Notes and/or stock)	50,447
Contingent earn-out liability (Cash and stock)	1,004
Total Consideration	51,451
Excess consideration over the amounts assigned to the net assets acquired (Goodwill)	25,141
Other Business Acquisitions | Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	10,423
Other Business Acquisitions | Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	1,365
Other Business Acquisitions | Customer backlog
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	1,363
Other Business Acquisitions | Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	0
Other Business Acquisitions | Other
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 814