Acquisition (Purchase Price Allocation) (Details) £ in Thousands, $ in Thousands	May 01, 2017 USD ($)	Apr. 06, 2017 GBP (£)	Sep. 29, 2017 USD ($)	Dec. 30, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill, net | $			$ 84,966	$ 72,376
Jibe Consulting, Inc [Member]
Business Acquisition [Line Items]
Total purchase consideration | $	$ 11,293
Accounts receivable | $	1,932
Other current assets | $	59
Total current assets acquired | $	1,991
Intangible assets | $	931
Goodwill, net | $	9,538
Total assets | $	12,460
Other accrued expenses | $	1,167
Total liabilities acquired | $	1,167
Purchase consideration on acquisition | $	$ 11,293
Aecus Limited [Member]
Business Acquisition [Line Items]
Total purchase consideration | £		£ 3,173
Cash | £		209
Accounts receivable | £		898
Other current assets | £		46
Total current assets acquired | £		1,153
Intangible assets | £		1,515
Goodwill, net | £		1,306
Total assets | £		3,974
Other accrued expenses | £		801
Total liabilities acquired | £		801
Purchase consideration on acquisition | £		£ 3,173