Enterprise-Wide Disclosures - Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2016	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Dec. 31, 2015	Oct. 02, 2015	Jul. 03, 2015	Apr. 03, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Enterprise-Wide Disclosures
Revenue		$ 77,492	$ 78,065	$ 83,486	$ 85,850	$ 84,202	$ 93,055	$ 94,744	$ 97,477	$ 324,893	$ 369,478	$ 393,268
Long-lived assets		5,863				5,488				5,863	5,488	6,793
Deferred tax assets, net of valuation allowance		6,886				6,406				$ 6,886	$ 6,406	$ 8,038
Threshold for Separate Geographic Disclosure										10.00%	10.00%	10.00%
Threshold for Long-lived Asset Geographic Disclosure										10.00%	10.00%	10.00%
United States [Member]
Enterprise-Wide Disclosures
Revenue										$ 253,955	$ 301,826	$ 314,500
Long-lived assets		4,280				4,208				4,280	4,208	5,759
Deferred tax assets, net of valuation allowance		6,886				6,352				6,886	6,352	7,982
Europe [Member]
Enterprise-Wide Disclosures
Deferred tax assets, net of valuation allowance		0				54				0	54	56
Belgium [Member]
Enterprise-Wide Disclosures
Revenue	[1]									35,995	35,931	44,692
Other European Countries [Member]
Enterprise-Wide Disclosures
Revenue										34,634	31,376	33,652
Long-lived assets		791				819				791	819	875
Other Country [Member]
Enterprise-Wide Disclosures
Revenue										309	345	424
Foreign Countries [Member]
Enterprise-Wide Disclosures
Revenue										70,938	67,652	78,768
United Kingdom [Member]
Enterprise-Wide Disclosures
Long-lived assets	[2]	$ 792				$ 461				$ 792	$ 461	$ 159

[1] Revenue for our Belgium operations has been disclosed separately as it exceeds 10% of consolidated revenue in at least one of the years presented.

[2] Long-lived assets for our United Kingdom operations has been disclosed separately as it exceeds 10% of consolidated long-lived assets in at least one of the years presented.