Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		3 Months Ended
		Apr. 01, 2017	Apr. 02, 2016
Cash flows from operating activities:
Net income (loss)		$ 2,968	$ (1,154)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation		1,058	1,455
Amortization of intangibles and other		536	643
Amortization of security premium		39	69
Stock-based compensation		3,192	3,479
Deferred income taxes		324	0
Changes in operating assets and liabilities:
Accounts receivable		(8,710)	(22,635)
Inventories		4,658	4,421
Prepaid expenses and other current assets		1,057	670
Other assets		(163)	(59)
Accounts payable		2,258	941
Deferred product and services income		756	1,651
Other current liabilities		(4,221)	2,029
Other liabilities		293	(404)
Net cash provided by (used in) operating activities		4,045	(8,894)
Cash flows from investing activities:
Capital expenditures		(555)	(185)
Purchase of investments in securities		(12,019)	(21,100)
Proceeds from maturities of investments		38,419	42,943
Net cash provided by investing activities		25,845	21,658
Cash flows from financing activities:
Proceeds from notes payable		1,500	5,120
Repayment of notes payable		(1,500)	(5,120)
Proceeds from issuance of common stock for stock option exercises		4,373	305
Tax payment for issuance of common stock from release of restricted stock units		(1,166)	(1,737)
Net cash provided by (used in) financing activities		3,207	(1,432)
Net increase in cash and cash equivalents		33,097	11,332
Cash and cash equivalents at beginning of period	[1]	86,744
Cash and cash equivalents at end of period		119,841	74,340
Other non-cash changes:
Systems transferred from (to) inventory to (from) equipment and other assets, net		$ 1,764	$ 0

[1] The balance sheet as of December 31, 2016 has been derived from the audited financial statements at that date.