Recent Accounting Pronouncements - Revenue From Contracts With Customers, Financial Statement Impact (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	$ 100,616	$ 92,014	$ 289,903	$ 257,272
Total cost of revenue	50,514	44,989	141,015	136,024
Gross Profit	50,102	47,025	148,888	121,248
Selling, general and administrative	29,723	37,121	88,874	104,377
Loss from operations	(3,651)	(14,206)	(12,336)	(62,786)
Loss before income taxes	(6,888)	(17,498)	(21,526)	(72,678)
Net loss	(7,758)	$ (15,583)	(24,365)	$ (71,110)
Accounts receivable, net	77,986		77,986			$ 69,844
Prepaid expenses and other current assets	24,226		24,226			18,931
Other long-term assets	38,624		38,624			42,913
Deferred revenue	48,679		48,679			52,429
Other non-current liabilities	18,989		18,989			22,626
Accumulated deficit	(2,070,746)		(2,070,746)			$ (2,057,812)
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net					$ 71,625
Prepaid expenses and other current assets					22,509
Other long-term assets					43,686
Deferred revenue					47,603
Other non-current liabilities					22,153
Accumulated deficit					(2,046,381)
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	100,382		288,419
Total cost of revenue	50,888		141,029
Gross Profit	49,494		147,390
Selling, general and administrative	29,680		89,221
Loss from operations	(4,216)		(14,181)
Loss before income taxes	(7,453)		(23,371)
Net loss	(8,323)		(26,210)
Accounts receivable, net	74,949		74,949
Prepaid expenses and other current assets	19,681		19,681
Other long-term assets	38,082		38,082
Deferred revenue	53,370		53,370
Other non-current liabilities	19,450		19,450
Accumulated deficit	(2,084,022)		(2,084,022)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	234		1,484
Total cost of revenue	(374)		(14)
Gross Profit	608		1,498
Selling, general and administrative	43		(347)
Loss from operations	565		1,845
Loss before income taxes	565		1,845
Net loss	565		1,845
Accounts receivable, net	3,037		3,037		1,781
Prepaid expenses and other current assets	4,545		4,545		3,578
Other long-term assets	542		542		773
Deferred revenue	(4,691)		(4,691)		(4,826)
Other non-current liabilities	(461)		(461)		(473)
Accumulated deficit	$ 13,276		$ 13,276		$ 11,431