Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows provided by (used in) operating activities:
Net income (loss)	$ (45,291)	$ (39,381)	$ 2,858
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization of property and equipment	968	910	1,016
Stock-based compensation	6,102	6,111	5,470
Deferred income taxes	(32)	24,274	9,935
Loss on disposal of equipment	1	19	4
Income from discontinued operations	0	(649)	0
Changes in operating assets and liabilities:
Accounts and other receivables	576	(171)	1,814
Prepaid income taxes	0	1,998	(6,995)
Prepaid expenses and other current assets	141	(86)	(1,945)
Intangibles and other assets	(197)	(275)	(36)
Accounts payable	696	5,322	(19)
Accrued compensation and other current liabilities	(1,111)	967	3,750
Deferred revenue	(5,575)	23,090	(6,394)
Other long-term liabilities	(107)	(87)	587
Net cash provided by (used in) operating activities	(43,829)	22,042	10,045
Cash flows provided by (used in) investing activities:
Purchases of short-term investments	(23,807)	(32,813)	(44,910)
Proceeds from maturities of short-term investments	35,000	40,000	48,000
Purchases of property and equipment	(125)	(343)	(4,430)
Proceeds from discontinued operations	0	1,000	0
Net cash provided by (used in) investing activities	11,068	7,844	(1,340)
Cash flows provided by financing activities:
Issuance of common stock under employee stock purchase plan	328	307	367
Exercise of stock options, net of shares withheld for employee taxes	518	2,388	1,561
Purchases of treasury stock	(328)	(729)	0
Net cash provided by financing activities	518	1,966	1,928
Net increase (decrease) in cash and cash equivalents	(32,243)	31,852	10,633
Cash and cash equivalents:
Beginning of year	56,865	25,013	14,380
End of year	24,622	56,865	25,013
Supplemental disclosure of cash flow information:
Cash paid for taxes	191	(419)	156
Supplemental disclosure of noncash operating, investing, and financing activities:
Amounts accrued for property and equipment	0	22	18
Cashless option exercise under company stock plan	0	177	69
Release of Restricted Stock Units and Awards under company stock plan	$ 2,661	$ 2,257	$ 3,059