Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Noncontrolling Interests [Member]
Beginning balance at Dec. 29, 2017	$ 300,305	$ 34	$ 185,302	$ 113,122	$ 1,847
Beginning balance, Shares at Dec. 29, 2017		33,664,940
Issuance under employee stock plans, Shares		387,071
Amortization of stock-based compensation	2,566		2,566
Employees’ taxes paid upon vesting of restricted stock units	(1,862)		(1,862)
Employees' taxes paid upon vesting of restricted stock units, Shares		(92,410)
Issuance of common stock in public offering	94,327	$ 5	94,322
Issuance of common stock in public offering, Shares		4,761,905
Net income (loss)	24,741			24,741
Other comprehensive loss	(541)				(541)
Ending balance at Mar. 30, 2018	419,536	$ 39	280,328	137,863	1,306
Ending balance, Shares at Mar. 30, 2018		38,721,506
Beginning balance at Dec. 29, 2017	300,305	$ 34	185,302	113,122	1,847
Beginning balance, Shares at Dec. 29, 2017		33,664,940
Net income (loss)	43,701
Ending balance at Jun. 29, 2018	439,327	$ 39	282,053	156,823	412
Ending balance, Shares at Jun. 29, 2018		38,926,652
Beginning balance at Mar. 30, 2018	419,536	$ 39	280,328	137,863	1,306
Beginning balance, Shares at Mar. 30, 2018		38,721,506
Issuance under employee stock plans	144		144
Issuance under employee stock plans, Shares		248,489
Amortization of stock-based compensation	2,337		2,337
Employees’ taxes paid upon vesting of restricted stock units	(756)		(756)
Employees' taxes paid upon vesting of restricted stock units, Shares		(43,343)
Net income (loss)	18,960			18,960
Other comprehensive loss	(894)				(894)
Ending balance at Jun. 29, 2018	439,327	$ 39	282,053	156,823	412
Ending balance, Shares at Jun. 29, 2018		38,926,652
Beginning balance at Dec. 28, 2018	450,988	$ 40	287,087	149,718	(547)	$ 14,690
Beginning balance, Shares at Dec. 28, 2018		39,065,935
Issuance under employee stock plans, Shares		296,142
Amortization of stock-based compensation	2,913		2,913
Employees’ taxes paid upon vesting of restricted stock units	(850)		(850)
Employees' taxes paid upon vesting of restricted stock units, Shares		(73,840)
Net income (loss)	1,354			605		749
Other comprehensive loss	(876)				(876)
Ending balance at Mar. 29, 2019	453,529	$ 40	289,150	150,323	(1,423)	15,439
Ending balance, Shares at Mar. 29, 2019		39,288,237
Beginning balance at Dec. 28, 2018	450,988	$ 40	287,087	149,718	(547)	14,690
Beginning balance, Shares at Dec. 28, 2018		39,065,935
Net income (loss)	1,100
Ending balance at Jun. 28, 2019	454,488	$ 40	291,595	150,121	(2,655)	15,387
Ending balance, Shares at Jun. 28, 2019		39,536,762
Beginning balance at Mar. 29, 2019	453,529	$ 40	289,150	150,323	(1,423)	15,439
Beginning balance, Shares at Mar. 29, 2019		39,288,237
Issuance under employee stock plans	125		125
Issuance under employee stock plans, Shares		296,549
Amortization of stock-based compensation	2,864		2,864
Employees’ taxes paid upon vesting of restricted stock units	(544)		(544)
Employees' taxes paid upon vesting of restricted stock units, Shares		(48,024)
Net income (loss)	(254)			(202)		(52)
Other comprehensive loss	(1,232)				(1,232)
Ending balance at Jun. 28, 2019	$ 454,488	$ 40	$ 291,595	$ 150,121	$ (2,655)	$ 15,387
Ending balance, Shares at Jun. 28, 2019		39,536,762