Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 29, 2014		Mar. 30, 2013
Cash flows from operating activities:
Net income (loss)	$ (6,971)		$ 13,692
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation	1,533		1,296
Amortization of intangibles and other	658		482
Amortization of security premium	96		153
Stock-based compensation	3,962		3,261
Changes in operating assets and liabilities:
Accounts receivable	2,962		1,582
Inventories	(1,025)		(6,597)
Prepaid expenses and other current assets	(158)		(970)
Other assets	(442)		(562)
Accounts payable	(386)		796
Deferred product and services income	(266)		(9,813)
Other current liabilities	(3,276)		(3,867)
Other liabilities	17		300
Net cash used in operating activities	(3,296)		(247)
Cash flows from investing activities:
Capital expenditures	(779)		(3,261)
Purchase of investments in securities	(62,111)		(74,826)
Proceeds from maturities of investments	54,303		54,426
Net cash used in investing activities	(8,587)		(23,661)
Cash flows from financing activities:
Proceeds from notes payable	5,120		1,000
Repayment of notes payable	(5,120)		(1,000)
Proceeds from issuance of common stock for stock option exercises	346		11,776
Tax payment for issuance of common stock from release of restricted stock units	(2,624)		(3,279)
Net cash provided by (used in) financing activities	(2,278)		8,497
Net decrease in cash and cash equivalents	(14,161)		(15,411)
Cash and cash equivalents at beginning of period	93,550	[1]	96,968
Cash and cash equivalents at end of period	79,389		81,557
Other non-cash changes:
Systems transferred from inventory and other assets to equipment, net	$ 240		$ 0

[1] The balance sheet as of December 31, 2013 has been derived from the audited financial statements at that date.