Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities
Net loss	$ (5,736)	$ (15,271)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	8,573	6,654
Employee stock-based compensation	15,257	14,102
Write-off of previously capitalized software costs	76	2,600
Impairment of assets held for sale and long-lived assets	22	56
Gain on disposal of property and equipment	35	(158)
Outside director restricted stock awarded in lieu of fees	150	150
Gain on sale of equity securities	(2,807)	(2,009)
Deferred tax benefit from unrealized gain on available-for-sale marketable securities, net	820
Changes in assets and liabilities:
Accounts receivable	(405)	3,482
Prepaid expenses and other assets	2,139	(1,456)
Accounts payable	5,725	(1,970)
Accrued compensation and employee benefits	(3,281)	2,436
Accrued expenses and other liabilities	890	2,428
Deferred revenues		(403)
Net cash provided by operating activities	21,458	10,641
Investing activities
Purchases of property and equipment	(10,403)	(8,788)
Proceeds from sale of property and equipment	10	8
Purchases of marketable securities	(88,152)	(56,504)
Maturities of marketable securities	59,402	51,257
Proceeds from sales of marketable securities	10,155	5,117
Other investments		(6,100)
Net cash used in investing activities	(28,988)	(15,010)
Financing activities
Net proceeds from issuance of common stock under stock plans	14,685	9,105
Withholding taxes related to restricted stock units net share settlement	(4,540)	(3,270)
Net cash provided by financing activities	10,145	5,835
Net increase in cash and cash equivalents	2,615	1,466
Cash and cash equivalents at the beginning of the period	40,404	32,533
Cash and cash equivalents at the end of the period	43,019	33,999
Non-cash investing and financing activities
Accrued purchases of property and equipment	$ 1,381	3,802
Change in fair value of equity investment		$ 942