Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands		Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 30, 2017		$ 28,489	$ 127,663	$ 150,726	$ (17,787)		$ 289,091
Cumulative effect of accounting change (a) at Dec. 30, 2017	[1]			1,057			1,057
Net income (loss)				8,122			8,122
Changes in cumulative translation adjustment					3,854		3,854
Adjustments related to postretirement benefits, net of tax					(73)		(73)
Changes in unrealized gains and losses on investments, net of tax					(10)		(10)
Cash dividends - $0.06 per share				(1,781)			(1,781)
Exercise of stock options		19	184				203
Shares issued for restricted stock units vested		448	(448)
Repurchase and retirement of stock		(160)	(3,620)				(3,780)
Share-based compensation expense			1,669				1,669
Balance at Mar. 31, 2018		28,796	125,448	158,124	(14,016)		298,352
Balance at Dec. 29, 2018		40,763	419,690	111,670	(25,880)	(299)	545,944	[2]
Cumulative effect of accounting change (a) at Dec. 29, 2018	[3]			10,352			10,352
Net income (loss)				(22,687)			(22,687)
Changes in cumulative translation adjustment					(5,258)	(4)	(5,262)
Adjustments related to postretirement benefits, net of tax					474		474
Changes in unrealized gains and losses on investments, net of tax
Cash dividends - $0.06 per share				(2,450)			(2,450)
Exercise of stock options		10	68				78
Shares issued for restricted stock units vested		365	(365)
Repurchase and retirement of stock		(123)	(1,705)				(1,828)
Share-based compensation expense			3,693				3,693
Noncontrolling interest				53		(53)
Balance at Mar. 30, 2019		$ 41,015	$ 421,381	$ 96,938	$ (30,664)	$ (356)	$ 528,314

[1] Cumulative effect of accounting change relates to our adoption of ASU 2014-09.

[2] Derived from December 29, 2018 audited financial statements

[3] Cumulative effect of accounting change relates to our adoption of ASU 2016-02. Please refer to Note 1 of the Condensed Consolidated Financial Statements for further detail on the adoption of this accounting standard.