Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jul. 04, 2021	Jun. 28, 2020
Cash flows from operating activities:
Net income	$ 147,446	$ 19,335
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	22,739	22,808
Depreciation of property, plant, and equipment	8,510	11,162
Loss on disposal of property, plant, and equipment	4	1,214
Amortization of intangible assets	1,853	2,582
Intangible asset impairment charges	0	19,571
Excess and obsolete inventory charges	1,816	8,783
Operating lease asset impairment charges	0	2,534
Amortization of discounts or premiums on investments	1,840	328
Realized gain on sale of investments	(68)	(2,805)
Credit loss on investments	0	75
Revaluation of contingent consideration	0	(114)
Change in deferred income taxes	973	1,395
Accounts receivable	(23,488)	(8,957)
Unbilled revenue	3,844	3,804
Inventories	(9,521)	(1,664)
Prepaid expenses and other current assets	(28,830)	(25,461)
Accounts payable	16,058	143
Accrued expenses	206	15,806
Accrued income taxes	(5,588)	(25,411)
Deferred revenue and customer deposits	55,220	32,586
Other	1,711	(1,534)
Net cash provided by operating activities	194,725	76,180
Cash flows from investing activities:
Purchases of investments	(511,625)	(317,540)
Maturities and sales of investments	270,696	387,765
Purchases of property, plant, and equipment	(6,550)	(6,985)
Net cash provided by (used in) investing activities	(247,479)	63,240
Cash flows from financing activities:
Net proceeds from issuance of common stock under stock plans	44,407	48,235
Repurchase of common stock	(20,877)	(51,036)
Payment of dividends	(21,192)	(18,972)
Payment of contingent consideration	0	(1,039)
Net cash provided by (used in) financing activities	2,338	(22,812)
Effect of foreign exchange rate changes on cash and cash equivalents	(1,620)	(2,018)
Net change in cash and cash equivalents	(52,036)	114,590
Cash and cash equivalents at beginning of period	269,073	171,431
Cash and cash equivalents at end of period	$ 217,037	$ 286,021