Geographic and Group Information (Revenue By Service Group) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 27, 2019	Sep. 28, 2018
Segment Reporting Information [Line Items]
Revenue before reimbursements from continuing operations	$ 72,690	$ 73,718	$ 213,366	$ 219,352
Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements from continuing operations	66,755	68,183	197,101	202,928
S&BT [Member] | Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements from continuing operations	27,435	26,014	78,632	76,931
EEA [Member] | Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements from continuing operations	30,920	29,971	89,049	89,145
International [Member] | Revenue Before Reimbursements [Member]
Segment Reporting Information [Line Items]
Revenue before reimbursements from continuing operations	$ 8,400	$ 12,198	$ 29,420	$ 36,852