Geographic and Group Information (Revenue By Service Group) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 29, 2019	Mar. 30, 2018
Segment Reporting Information [Line Items]
Revenue before reimbursements	$ 67,155	$ 71,107
Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements	62,370	66,039
S&BT [Member] \| Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements	33,270	35,139
EEA [Member] \| Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements	$ 29,100	$ 30,900

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration