Financial Information by Quarter (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 26, 2020	Sep. 26, 2020	Jun. 27, 2020	Mar. 28, 2020	Dec. 28, 2019	Sep. 28, 2019	Jun. 29, 2019	Mar. 30, 2019	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
Revenue:
Revenue	$ 353,525	$ 340,211	$ 331,587	$ 330,273	$ 384,567	$ 325,341	$ 296,250	$ 292,707	$ 1,355,596	$ 1,298,865	$ 943,379
Cost of revenue:
Amortization of intangible assets	4,611	7,287	8,721	8,628	8,437	7,796	8,098	8,252	29,247	32,583	23,475
Acquisition and integration costs	0	43	750	1,035	7,238	8,447	10,700	2,064	1,828	28,449	0
Restructuring and related	(106)	1,504	1,591	1,157	5,407	1,198	1,864	21,466	4,146	29,935	2,630
Total cost of revenue	227,382	231,935	234,180	253,307	273,161	238,512	234,994	226,275	946,804	972,942	622,223
Gross profit	126,143	108,276	97,407	76,966	111,406	86,829	61,256	66,432	408,792	325,923	321,156
Amortization of intangible assets	4,745	4,696	4,585	4,555	6,617	6,861	6,745	7,057	18,581	27,280	29,296
Acquisition and integration costs	(265)	1,045	3,344	9,222	11,011	11,962	12,164	7,134	13,346	42,271	15,530
Restructuring and related	7,230	6,679	5,097	5,580	18,024	2,168	3,471	17,188	24,586	40,851	12,512
Other operating expenses	121,209	122,773	129,007	134,489	136,625	135,125	147,260	146,741
Total operating expenses	132,919	135,193	142,033	153,846	172,277	156,116	169,640	178,120	563,991	676,153	506,835
Loss from operations	(6,776)	(26,917)	(44,626)	(76,880)	(60,871)	(69,287)	(108,384)	(111,688)	(155,199)	(350,230)	(185,679)
Other income (expense), net	(2,043)	(7,620)	(14,374)	(21,452)	(5,886)	(13,932)	(3,887)	(9,720)	(45,489)	(33,425)	(29,271)
Loss before income taxes	(8,819)	(34,537)	(59,000)	(98,332)	(66,757)	(83,219)	(112,271)	(121,408)	(200,688)	(383,655)	(214,950)
Provision for (benefit from) income taxes	1,105	1,359	2,635	936	(163)	1,548	1,385	193	6,035	2,963	(655)
Net loss	$ (9,924)	$ (35,896)	$ (61,635)	$ (99,268)	$ (66,594)	$ (84,767)	$ (113,656)	$ (121,601)	$ (206,723)	$ (386,618)	$ (214,295)
Net loss per common share
Basic (in usd per share)	$ (0.05)	$ (0.19)	$ (0.33)	$ (0.55)	$ (0.37)	$ (0.47)	$ (0.64)	$ (0.69)	$ (1.10)	$ (2.16)	$ (1.36)
Diluted (in usd per share)	$ (0.05)	$ (0.19)	$ (0.33)	$ (0.55)	$ (0.37)	$ (0.47)	$ (0.64)	$ (0.69)	$ (1.10)	$ (2.16)	$ (1.36)
Product
Revenue:
Revenue	$ 267,226	$ 261,906	$ 261,227	$ 255,192	$ 307,861	$ 253,754	$ 226,866	$ 223,007	$ 1,045,551	$ 1,011,488	$ 763,555
Cost of revenue:
Cost of revenue	178,153	185,001	186,519	201,792	213,536	186,205	177,501	157,817	751,465	735,059	517,765
Services
Revenue:
Revenue	86,299	78,305	70,360	75,081	76,706	71,587	69,384	69,700	310,045	287,377	179,824
Cost of revenue:
Cost of revenue	$ 44,724	$ 38,100	$ 36,599	$ 40,695	$ 38,543	$ 34,866	$ 36,831	$ 36,676	$ 160,118	$ 146,916	$ 78,353