CONSOLIDATED STATEMENTS OF CASH FLOWS Non-Cash Activities - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Other Significant Noncash Transactions [Line Items]
Unrealized (loss) gain on available-for-sale securities	$ (233)	$ 22
Common Stock Issued To Board Of Directors And Scientific Advisory Board That Was Earned In Previous Period [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received	300	300
Common Stock Issued To Employees That Was Accrued For In Previous Period Net Of Shares Withheld For Taxes [Member]
Other Significant Noncash Transactions [Line Items]
Other significant noncash transaction, value of consideration received	1,105	967
Other Capitalized Property Plant and Equipment [Member]
Other Significant Noncash Transactions [Line Items]
Net change in accounts payable and accrued expenses related to purchases of property and equipment	$ 343	$ (686)