Condensed Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock Including Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning Balance at Dec. 31, 2017		$ 80,336	$ 161,364	$ (6,117)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised		1,397
Stock awards vested		2,724
Stock repurchased related to the exercise of stock options		(5,467)
Stock-based compensation		3,571
Net Income	$ 8,362
Other Comprehensive Income, Net of Tax	1,017			1,017
Ending Balance at Sep. 29, 2018	255,826	82,561	179,683	(6,418)
Beginning Balance at Jun. 30, 2018		81,445	175,512	(6,687)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock options exercised		539
Stock awards vested		7
Stock repurchased related to the exercise of stock options		(729)
Stock-based compensation		1,299
Net Income	4,171
Other Comprehensive Income, Net of Tax	269			269
Ending Balance at Sep. 29, 2018	255,826	82,561	179,683	(6,418)
Beginning Balance at Dec. 31, 2018	256,825	83,826	180,356	(7,357)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee Stock Purchase Plan		1,118
Stock options exercised		1,409
Stock awards vested		6,665
Stock repurchased related to the exercise of stock options		(11,396)
Stock-based compensation		5,322
Net Income	23,590
Other Comprehensive Income, Net of Tax	510			510
Ending Balance at Sep. 28, 2019	283,779	86,944	203,682	(6,847)
Beginning Balance at Jun. 29, 2019		83,959	195,379	(7,108)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee Stock Purchase Plan		1,118
Stock options exercised		570
Stock awards vested		30
Stock repurchased related to the exercise of stock options		(784)
Stock-based compensation		2,051
Net Income	8,303
Other Comprehensive Income, Net of Tax	261			261
Ending Balance at Sep. 28, 2019	$ 283,779	$ 86,944	$ 203,682	$ (6,847)