CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows From Operating Activities:
Net Loss	$ (12,625)	$ (17,239)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	1,165	1,352
Amortization and Premium of Marketable Securities, Net	(63)	(345)
Loss on Sale or Disposal of Assets		25
Other Asset Impairment		1,800
Gain on Fair Value Remeasurement of Contingent Consideration	234	1,519
Stock-Based Compensation Expense	687	1,693
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	(93)	855
Prepaid and Other Current Assets	206	299
Accounts Payable and Accrued Expenses	(853)	(1,455)
Other Liabilities	(768)	(1,737)
Net Cash Used in Operating Activities	(12,110)	(13,233)
Cash Flows From Investing Activities:
Sales and Maturities of Marketable Securities	22,200	37,886
Purchases of Marketable Securities		(21,404)
Acquisition of Property and Equipment	(235)	(186)
Net Cash Provided by Investing Activities	21,965	16,296
Cash Flows From Financing Activities:
Net Proceeds from Stock Issuances	1,613	4,151
Proceeds from Issuance of Stock from Employee Benefit Plans	24	9
Net Cash Provided by Financing Activities	1,637	4,160
Net Decrease in Cash and Cash Equivalents	11,492	7,223
Cash and Cash Equivalents at Beginning of Period	11,232	11,232
Cash and Cash Equivalents at End of Period	22,724	31,533
Non-cash Investing Activities
Accrued construction in progress	$ 462	$ 65