Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Treasury Shares	Retained Earnings
Balance at Dec. 28, 2018	$ 198,326	$ 2	$ 228,358	$ (89,979)	$ 59,945
Balance, Shares at Dec. 28, 2018		22,234,508		4,339,529
Ordinary shares issued from exercise of stock options	1,904		1,904
Ordinary shares issued from exercise of stock options, shares		186,915
Ordinary shares issued from vesting of restricted share units	(111)		(111)
Ordinary shares issued from vesting of restricted share units, shares		24,115
Ordinary shares issued from employee share purchase plan	312		312
Ordinary shares issued from employee share purchase plan, shares		22,501
Repurchase of ordinary shares	(1,599)			$ (1,599)
Repurchase of ordinary shares, shares		(97,910)		97,910
Share-based compensation expense	1,330		1,330
Net income	1,518				1,518
Balance at Mar. 29, 2019	201,680	$ 2	231,793	$ (91,578)	61,463
Balance, Shares at Mar. 29, 2019		22,370,129		4,437,439
Balance at Dec. 27, 2019	221,416	$ 2	242,318	$ (91,578)	70,674
Balance, Shares at Dec. 27, 2019		22,618,708		4,437,439
Ordinary shares issued from exercise of stock options	2,483		2,483
Ordinary shares issued from exercise of stock options, shares		113,539
Ordinary shares issued from vesting of restricted share units	(993)		(993)
Ordinary shares issued from vesting of restricted share units, shares		57,912
Ordinary shares issued from employee share purchase plan	350		350
Ordinary shares issued from employee share purchase plan, shares		16,520
Share-based compensation expense	2,865		2,865
Net income	3,399				3,399
Balance at Mar. 27, 2020	$ 229,520	$ 2	$ 247,023	$ (91,578)	$ 74,073
Balance, Shares at Mar. 27, 2020		22,806,679		4,437,439