CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net loss	$ (4,997)	$ (7,215)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	211	258
Stock-based compensation	888	1,043
Amortization of intangible assets	250	683
Gain on sale of assets	(630)	(1,856)
Other non-cash items	5
Changes in assets and liabilities:
Accounts receivable	219	661
Prepaid expenses and other assets	(98)	81
Deferred revenue	(145)	(45)
Accounts payable	1,202	(39)
Accrued expenses and other liabilities	(1,892)	201
Net cash used in operating activities	(4,987)	(6,228)
Cash flows from investing activities:
Purchases of property and equipment	(57)	(25)
Net proceeds from sale of assets	630	2,187
Proceeds from sales and maturities of marketable securities	15,589	8,454
Purchases of marketable securities	(9,433)	(35,793)
Net cash provided by (used in) investing activities	6,729	(25,177)
Cash flows from financing activities:
Proceeds from issuance of common stock	1,008	847
Payments on capital lease obligations		(47)
Net cash provided by financing activities	1,008	800
Net increase (decrease) in cash and cash equivalents	2,750	(30,605)
Cash and cash equivalents at beginning of period	2,529	40,025
Cash and cash equivalents at end of period	$ 5,279	$ 9,420

Name:	us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.