CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows provided by (used in) operating activities:
Net income (loss)	$ (21,023)	$ 57,485
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	588	647
Stock-based compensation	4,371	6,266
Foreign currency translation loss	361	0
Deferred income taxes	105	67
Other	1	26
Changes in operating assets and liabilities:
Accounts and other receivables	(814)	(454)
Prepaid expenses and other current assets	(2,239)	(1,870)
Other assets	(9,849)	(3,910)
Accounts payable	(1,440)	(5,889)
Accrued compensation	(1,567)	(1,560)
Other current liabilities	(15)	1,807
Deferred revenue	(3,312)	22,713
Other long-term liabilities	3,967	211
Net cash provided by (used in) operating activities	(30,866)	75,539
Cash flows provided by investing activities:
Purchases of short-term investments	(8,930)	(17,693)
Proceeds from maturities of short-term investments	14,000	22,000
Purchases of property and equipment	(12)	(63)
Net cash provided by investing activities	5,058	4,244
Cash flows provided by financing activities:
Proceeds from issuance of common stock under employee stock purchase plan	165	218
Proceeds from stock options exercises	1,240	8,010
Net cash provided by financing activities	1,405	8,228
Net increase (decrease) in cash and cash equivalents	(24,403)	88,011
Cash and cash equivalents:
Beginning of period	110,988	24,622
End of period	86,585	112,633
Supplemental disclosure of cash flow information:
Cash paid for income taxes	104	139
Supplemental disclosure of non-cash operating, investing, and financing activities:
Release of restricted stock units and awards under company stock plan	$ 7,148	$ 2,806