Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 43,019	$ 40,404
Short-term marketable securities	75,942	56,585
Accounts receivable (net of allowance for doubtful accounts; 2017—$3,599, 2016—$4,508)	35,584	35,179
Prepaid expenses and other current assets	11,506	13,796
Total current assets	166,051	145,964
Property and equipment, net	47,411	45,688
Other assets	9,522	9,462
Total assets	222,984	201,114
Current liabilities:
Accounts payable	8,475	2,864
Accrued compensation and employee benefits	24,619	27,900
Accrued expenses and other current liabilities	11,116	10,180
Other current liabilities	212	231
Total current liabilities	44,422	41,175
Other liabilities	3,867	3,834
Commitments and contingencies
Stockholders' equity:
Common stock	3	3
Additional paid- in capital	452,653	427,102
Accumulated other comprehensive (loss) income	(27)	1,198
Accumulated deficit	(247,824)	(242,088)
Treasury stock, at cost	(30,110)	(30,110)
Total stockholders' equity	174,695	156,105
Total liabilities and stockholders' equity	$ 222,984	$ 201,114

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Name:	us-gaap_AccountsPayableCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.