Unaudited Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 839	$ (5,230)	$ 13,682	$ 360
Other comprehensive income (loss), before tax:
Change in unrealized gains and losses on derivatives	(2)	124	21	816
Change in unrealized gains and losses on available-for-sale investments	1	69	16	31
Other comprehensive income (loss), before tax	(1)	193	37	847
Tax provision related to derivatives	0	(15)	(6)	(76)
Tax provision related to available-for-sale investments	(1)	(16)	(4)	(27)
Other comprehensive income (loss), net of tax	(2)	162	27	744
Comprehensive income (loss)	$ 837	$ (5,068)	$ 13,709	$ 1,104