CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net loss	$ (32,682)	$ (24,794)	$ (27,614)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	449	679	952
Amortization of intangible assets	1,000	999	1,746
Stock-based compensation	4,591	3,698	3,811
Gain on sale of assets		(630)	(3,291)
Other non-cash items		7
Changes in assets and liabilities:
Accounts receivable	(29)	139	682
Inventories	(314)	(315)	(252)
Prepaid expenses and other assets	405	1	623
Accounts payable	(23)	(125)	(84)
Accrued expenses and other liabilities	296	(2,304)	1,411
Net cash used in operating activities	(26,307)	(22,645)	(22,016)
Cash flows from investing activities:
Purchases of property and equipment	(596)	(154)	(738)
Net proceeds from sale of assets		630	3,437
Proceeds from sales and maturities of marketable securities	39,270	49,267	34,371
Purchases of marketable securities	(15,859)	(57,202)	(54,592)
Net cash provided by ( used in ) investing activities	22,815	(7,459)	(17,522)
Cash flows from financing activities:
Proceeds from the sale of common stock, net of issuance costs		27,746
Net proceeds from issuance of common stock	2,238	4,193	3,636
Repurchase of common stock			(1,444)
Payments on capital lease obligations			(150)
Net cash provided by financing activities	2,238	31,939	2,042
Net increase (decrease) in cash and cash equivalents	(1,254)	1,835	(37,496)
Cash and cash equivalents at beginning of year	3,110	4,364	2,529
Supplemental disclosure:
Cash paid for income taxes	$ 111	$ 92	$ 345