Summary of Significant Accounting Policies - Basic and Diluted Earning (Loss) Per Share (EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 29, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jul. 01, 2016	Apr. 01, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income (loss)	$ (419)	$ 40	$ 434	$ 751	$ 1,143	$ (16,183)	$ 1,259	$ (20,857)	$ 806	$ (34,638)	$ 6,510
Weighted average number of shares outstanding, basic (in shares)									15,055	15,593	15,479
Basic (in dollars per share)	$ (0.03)	$ 0.00	$ 0.03	$ 0.05	$ 0.07	$ (1.03)	$ 0.08	$ (1.34)	$ 0.05	$ (2.22)	$ 0.42
Number of shares, attributable to equity based compensation plans (in shares)									269		441
Dilutive effect on basic earnings (loss) per share (in dollars per share)									$ 0.00		$ (0.01)
Weighted average number of shares outstanding, diluted (in shares)									15,324	15,593	15,920
Diluted (in dollars per share)	$ (0.03)	$ 0.00	$ 0.03	$ 0.05	$ 0.07	$ (1.03)	$ 0.08	$ (1.34)	$ 0.05	$ (2.22)	$ 0.41