Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ 2,577,000	$ (4,440,000)	$ (10,612,000)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Stock-based compensation	3,713,000	4,084,000	3,299,000
Depreciation and amortization	982,000	1,186,000	1,336,000
Impairment of intangible assets			650,000
Other	15,000	227,000	206,000
Changes in assets and liabilities:
Accounts receivable	(4,899,000)	(536,000)	(1,460,000)
Inventories	(2,899,000)	(1,090,000)	(1,982,000)
Other current assets and prepaid expenses	(432,000)	241,000	239,000
Other long-term assets	4,000	(23,000)	(37,000)
Accounts payable	639,000	(1,124,000)	1,263,000
Accrued liabilities	3,461,000	2,687,000	1,650,000
Other long-term liabilities	(329,000)	(289,000)	(285,000)
Deferred revenue	(826,000)	(2,319,000)	1,410,000
Income tax liability	(14,000)	37,000	37,000
Net cash provided by (used in) operating activities	1,992,000	(1,359,000)	(4,286,000)
Cash flows from investing activities:
Acquisition of property, equipment and software	(537,000)	(746,000)	(734,000)
Disposal of property and equipment	20,000
Proceeds from sales of marketable investments	9,008,000	21,171,000	12,354,000
Proceeds from maturities of marketable investments	25,810,000	35,918,000	26,915,000
Purchase of marketable investments	(37,693,000)	(23,697,000)	(44,146,000)
Net cash provided by (used in) investing activities	(3,392,000)	32,646,000	(5,611,000)
Cash flows from financing activities:
Repurchase of common stock	(4,873,000)	(40,085,000)
Proceeds from exercise of stock options and employee stock purchase plan	10,111,000	11,079,000	3,758,000
Taxes paid related to net share settlement of equity awards	(618,000)	(1,018,000)	(156,000)
Payments on capital lease obligation	(313,000)	(198,000)	(144,000)
Net cash provided by (used in) financing activities	4,307,000	(30,222,000)	3,458,000
Net increase (decrease) in cash and cash equivalents	2,907,000	1,065,000	(6,439,000)
Cash and cash equivalents at beginning of year	10,868,000	9,803,000	16,242,000
Cash and cash equivalents at end of year	13,775,000	10,868,000	9,803,000
Supplemental cash flow information:
Cash paid for interest	43,000	20,000	26,000
Cash paid for income taxes	222,000	160,000	225,000
Supplemental non-cash investing and financing activities:
Assets acquired under capital lease	$ 801,000	$ 285,000	$ 70,000