Stockholders' Equity - Summary of Changes In Stockholders' Equity (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jul. 01, 2018	Apr. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Value, Issued beginning balance		$ 0			$ 0
Capital in excess of par value beginning balance		359,570,000			359,570,000
Retained earnings beginning balance		(115,660,000)			(115,660,000)
Accumulated other comprehensive income beginning balance	$ (1,624,000)				(1,624,000)
Beginning Balance	263,788,000	242,571,000	$ 274,592,000	$ 262,148,000	242,571,000	$ 262,148,000
Net income (loss)	(8,734,000)	21,246,000	(8,965,000)	12,223,000	12,512,000	3,256,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(130,000)		145,000		(285,000)	300,000
Total components of other comprehensive income (loss), net of tax	(130,000)	(155,000)	145,000	154,000
Stock-based compensation costs	171,000	126,000	166,000	67,000
Common Stock, Value, Issued ending balance	0				0
Capital in excess of par value ending balance	359,867,000				359,867,000
Retained earnings ending balance	(103,148,000)				(103,148,000)
Accumulated other comprehensive income ending balance		(1,339,000)			(1,339,000)
Ending Balance	$ 255,095,000	$ 263,788,000	$ 265,938,000	$ 274,592,000	$ 255,095,000	$ 265,938,000
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance (in shares)	200	200	200	200	200	200
Common Stock, Value, Issued beginning balance	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Ending Balance (in shares)	200	200	200	200	200	200
Common Stock, Value, Issued ending balance	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Capital in excess of par value beginning balance	359,696,000	359,570,000	359,300,000	359,233,000	359,570,000	359,233,000
Stock-based compensation costs	171,000	126,000	166,000	67,000
Capital in excess of par value ending balance	359,867,000	359,696,000	359,466,000	359,300,000	359,867,000	359,466,000
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Retained earnings beginning balance	(94,414,000)	(115,660,000)	(82,976,000)	(95,199,000)	(115,660,000)	(95,199,000)
Net income (loss)	(8,734,000)	21,246,000	(8,965,000)	12,223,000
Retained earnings ending balance	(103,148,000)	(94,414,000)	(91,941,000)	(82,976,000)	(103,148,000)	(91,941,000)
Accumulated Other Comprehensive Income (Loss) [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accumulated other comprehensive income beginning balance	(1,624,000)	(1,494,000)	(1,587,000)	(1,732,000)	(1,624,000)	(1,587,000)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	(130,000)	(155,000)	145,000	154,000
Accumulated other comprehensive income ending balance	$ (1,494,000)	$ (1,339,000)	$ (1,732,000)	$ (1,886,000)	$ (1,339,000)	$ (1,886,000)