CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) Non-Cash Activities - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Other Significant Noncash Transactions [Line Items]
Unrealized loss on available-for-sale securities	$ 8	$ 58
Common stock issued to Board of Directors and Scientific Advisory Board that was earned and accrued for in a previous period
Other Significant Noncash Transactions [Line Items]
Other significant noncash transactions	300	323
Common stock issued to employees that was earned and accrued for in a previous period
Other Significant Noncash Transactions [Line Items]
Other significant noncash transactions	967	746
Net change in accounts payable and accrued expenses related to purchases of property and equipment
Other Significant Noncash Transactions [Line Items]
Other significant noncash transactions	$ (725)	$ 64