CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash Flows From Operating Activities:
Net Loss	$ (50,878)	$ (151,184)	$ (93,031)
Adjustments to Reconcile Net Loss to Net Cash Used in Operating Activities:
Depreciation and Amortization	4,858	3,577	4,414
Amortization of Intangible Assets		224	896
Amortization and Premium of Marketable Securities, Net	(1,140)	(1,048)	(290)
Loss on Sale or Disposal of Assets	11	1,220	55
Goodwill Impairment		90,976
Intangible Asset Impairment		18,677	13,000
Other Asset Impairment	1,800
Gain on Fair Value Remeasurement of Contingent Consideration	(1,294)	(29,621)	(800)
Non-Cash Income Tax Benefit		(765)	(24,282)
Stock-Based Compensation Expense	4,551	8,081	12,312
Changes in Operating Assets and Liabilities:
Accounts and Other Receivables	2,274	(777)	(96)
Prepaid and Other Current Assets	362	1,783	793
Other Assets	(39)		205
Accounts Payable and Accrued Expenses	(321)	(13,110)	(8,744)
Other Liabilities	(6,599)	(3,268)	(4,363)
Net Cash Used in Operating Activities	(46,415)	(75,235)	(99,931)
Cash Flows From Investing Activities:
Sales and Maturities of Marketable Securities	113,173	201,469	219,236
Purchases of Marketable Securities	(95,382)	(171,182)	(170,980)
Acquisition of Property and Equipment	(731)	(813)	(1,788)
Proceeds from Sale or Disposal of Assets	20	342
Net Cash Provided by Investing Activities	17,080	29,816	46,468
Cash Flows From Financing Activities:
Net Proceeds from Stock Issuances	16,248	29,022	51,025
Proceeds from Issuance of Stock from Employee Benefit Plans	9	419	265
Net Cash Provided by Financing Activities	16,257	29,441	51,290
Net Decrease in Cash and Cash Equivalents	(13,078)	(15,978)	(2,173)
Cash and Cash Equivalents at Beginning of Period	24,310	40,288	42,461
Cash and Cash Equivalents at End of Period	11,232	24,310	40,288
Non-cash Investing Activities
Accrued construction in progress	$ 25	107	20
Non-cash Supplemental Disclosure
Shares issued to former Kolltan executive for settlement of severance		$ 71	$ 344