CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Cumulative Effect, Period Of Adoption, Adjustment	Dividend Declared	Dividend Paid	Common Stock	Additional Paid-in Capital	Retained Earnings	Retained Earnings Cumulative Effect, Period Of Adoption, Adjustment	Retained Earnings Dividend Declared	Retained Earnings Dividend Paid	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period Of Adoption, Adjustment	Non-controlling Interest
Beginning balance at Dec. 29, 2018	$ 563,259				$ 43,582	$ 18,041	$ 504,909				$ (3,599)		$ 326
Beginning balance (Accounting Standards Update 2018-02) at Dec. 29, 2018		$ 0						$ 739				$ (739)
Beginning balance (Accounting Standards Update 2016-02) at Dec. 29, 2018	2,999						2,999
Comprehensive income:
Net income (loss)	62,908						62,910						(2)
Other comprehensive income (loss), net of tax	(2,712)										(2,712)
Dividends	(39,164)						(39,164)
Common shares – treasury:
Shares purchased	(64,877)				(1,797)	(36,401)	(26,679)
Shares issued under Members' Stock Purchase Plan and stock awards, net of tax	37,932				1,039	36,893
Ending balance at Sep. 28, 2019	560,345				42,824	18,534	505,714				(7,050)		323
Beginning balance at Dec. 29, 2018	563,259				43,582	18,041	504,909				(3,599)		326
Beginning balance (Accounting Standards Update 2018-02) at Dec. 29, 2018		0						739				$ (739)
Beginning balance (Accounting Standards Update 2016-02) at Dec. 29, 2018	2,999						2,999
Ending balance at Dec. 28, 2019	$ 584,368	(131)			42,595	19,799	529,723	(131)			(8,073)		324
Common shares – treasury:
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance at Jun. 29, 2019	$ 529,509				42,875	17,364	474,519				(5,574)		325
Comprehensive income:
Net income (loss)	46,076						46,078						(2)
Other comprehensive income (loss), net of tax	(1,476)										(1,476)
Dividends	(13,088)						(13,088)
Common shares – treasury:
Shares purchased	(7,191)				(221)	(5,175)	(1,795)
Shares issued under Members' Stock Purchase Plan and stock awards, net of tax	6,515				170	6,345
Ending balance at Sep. 28, 2019	560,345				42,824	18,534	505,714				(7,050)		323
Beginning balance at Dec. 28, 2019	584,368	$ (131)			42,595	19,799	529,723	$ (131)			(8,073)		324
Comprehensive income:
Net income (loss)	19,346						19,349						(3)
Other comprehensive income (loss), net of tax	(1,756)										(1,756)
Dividends			$ (175)	$ (39,060)					$ (175)	$ (39,060)
Common shares – treasury:
Shares purchased	(6,390)				(214)	(4,988)	(1,188)
Shares issued under Members' Stock Purchase Plan and stock awards, net of tax	17,388				334	17,054
Ending balance at Sep. 26, 2020	$ 573,590				42,715	31,865	508,518				(9,829)		321
Common shares – treasury:
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Beginning balance at Jun. 27, 2020	$ 553,069				42,675	29,988	490,909				(10,825)		322
Comprehensive income:
Net income (loss)	30,687						30,688						(1)
Other comprehensive income (loss), net of tax	996										996
Dividends			$ (58)	$ (13,021)					$ (58)	$ (13,021)
Common shares – treasury:
Shares issued under Members' Stock Purchase Plan and stock awards, net of tax	1,917				40	1,877
Ending balance at Sep. 26, 2020	$ 573,590				$ 42,715	$ 31,865	$ 508,518				$ (9,829)		$ 321