Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014
Operating activities:
Net loss	$ (16,787)	$ (17,826)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	7,602	6,772
Loss on retirement of property and equipment	14	41
Amortization of intangible assets	13,920	13,921
Amortization of premiums related to available-for-sale securities	743	302
Gain on sale of available-for-sale securities	0	(1)
Stock-based compensation	10,593	12,119
Changes in operating assets and liabilities:
Restricted cash	295	0
Accounts receivable, net	(17,443)	739
Inventory	2,983	7,226
Deferred cost of revenue	2,082	9,742
Prepaid expenses and other assets	4,181	(315)
Accounts payable	(6,841)	(9,904)
Accrued liabilities	(1,055)	5,520
Deferred revenue	(1,312)	(14,391)
Other long-term liabilities	(167)	597
Net cash provided by (used in) operating activities	(1,192)	14,542
Investing activities:
Purchases of property and equipment	(5,943)	(9,481)
Purchases of marketable securities	(46,750)	(49,356)
Sales of marketable securities	0	615
Maturities of marketable securities	51,265	0
Net cash used in investing activities	(1,428)	(58,222)
Financing activities:
Proceeds from exercise of stock options	625	429
Proceeds from employee stock purchase plan	2,865	2,453
Payments for repurchases of common stock	(11,124)	0
Taxes paid for awards vested under equity incentive plans	(2,093)	(2,505)
Net cash provided by (used in) financing activities	(9,727)	377
Effect of exchange rate changes on cash and cash equivalents	(288)	(45)
Net decrease in cash and cash equivalents	(12,635)	(43,348)
Cash and cash equivalents at beginning of period	48,829	82,747
Cash and cash equivalents at end of period	$ 36,194	$ 39,399