Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities
Net loss	$ (3,775)	$ (806)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	3,155	2,407
Employee stock-based compensation	5,186	5,105
Write-off of previously capitalized software costs	2,368
Impairment of long-lived assets	2,154
Gain on disposal of property and equipment		35
Outside director restricted stock awarded in lieu of fees	50	50
Gain on sale of equity securities		(2,807)
Unrealized gain on revaluation of equity investment	(127)
Accretion of discount on convertible promissory note	(62)
Deferred tax benefit from unrealized gain on available-for-sale marketable securities, net		820
Changes in assets and liabilities:
Accounts receivable	(1,283)	586
Prepaid expenses and other assets	(786)	722
Accounts payable	4,591	2,218
Accrued compensation and employee benefits	(3,040)	(8,791)
Accrued expenses and other liabilities	(2,151)	1,231
Net cash provided by operating activities	6,280	770
Investing activities
Purchases of property and equipment	(2,236)	(5,144)
Proceeds from sale of property and equipment		10
Purchases of marketable securities	(24,043)	(20,599)
Maturities of marketable securities	20,019	13,250
Proceeds from sales of marketable securities		10,155
Net cash used in investing activities	(6,260)	(2,328)
Financing activities
Proceeds from issuance of common stock under stock plans	1,152	6,069
Withholding taxes related to restricted stock units net share settlement	(4,601)	(4,136)
Net cash (used in) provided by financing activities	(3,449)	1,933
Net (decrease) increase in cash, cash equivalents and restricted cash	(3,429)	375
Cash, cash equivalents and restricted cash at the beginning of period	45,708	40,585
Cash, cash equivalents and restricted cash at the end of period	42,279	40,960
Non-cash investing and financing activities
Accrued purchases of property and equipment	533	$ 2,486
Change in fair value of equity investment	$ 200