Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 42,200	$ 40,404
Short-term marketable securities	67,599	56,585
Accounts receivable (net of allowance for doubtful accounts; 2017—$3,106, 2016—$4,508)	32,427	35,179
Prepaid expenses and other current assets	12,278	13,796
Total current assets	154,504	145,964
Property and equipment, net	48,908	45,688
Other assets	9,518	9,462
Total assets	212,930	201,114
Current liabilities:
Accounts payable	5,322	2,864
Accrued compensation and employee benefits	21,355	27,900
Accrued expenses and other current liabilities	12,185	10,180
Other current liabilities	222	231
Total current liabilities	39,084	41,175
Other liabilities	3,899	3,834
Commitments and contingencies
Stockholders' equity:
Common stock	3	3
Additional paid- in capital	445,713	427,102
Accumulated other comprehensive (loss) income	(26)	1,198
Accumulated deficit	(245,633)	(242,088)
Treasury stock, at cost	(30,110)	(30,110)
Total stockholders' equity	169,947	156,105
Total liabilities and stockholders' equity	$ 212,930	$ 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.