Condensed Consolidated Statements of Cash Flows - USD ($)	3 Months Ended				12 Months Ended			51 Months Ended
	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (14,423,000)	$ (13,674,000)	$ (12,558,000)	$ (11,592,000)	$ (53,240,000)	$ (47,149,000)	$ (51,508,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash royalty revenue related to royalty monetization					(312,000)	(289,000)	(151,000)
Non-cash interest (income) expense on liability related to royalty monetization					(1,337,000)	10,341,000	10,721,000	$ 31,535,000
Depreciation and amortization					1,668,000	575,000	1,744,000
Non-cash interest expense related to debt financing					712,000	613,000	1,265,000
Stock-based compensation					5,057,000	5,168,000	4,294,000
Inventory impairment charge					951,000		369,000
Other					(773,000)	(201,000)	(198,000)
Changes in operating assets and liabilities:
Accounts receivable					(383,000)	1,484,000	4,300,000
Inventories					(3,392,000)	102,000	920,000
Prepaid expenses and other assets					(465,000)	(850,000)	175,000
Tax receivable					352,000		(703,000)
Other assets					(220,000)
Accounts payable					(19,000)	458,000	309,000
Accrued liabilities					1,141,000	922,000	(1,301,000)
Operating lease liabilities					(701,000)
Deferred revenue					(219,000)	(362,000)	(361,000)
Deferred rent						113,000	360,000
Net cash used in operating activities					(51,180,000)	(29,075,000)	(29,765,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment					(3,470,000)	(819,000)	(2,405,000)
Purchase of investments					(100,068,000)	(30,558,000)	(7,565,000)
Proceeds from maturities of investments					66,975,000	20,500,000
Net cash used in investing activities					(36,563,000)	(10,877,000)	(9,970,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of long-term debt					25,000,000
Payment of costs in connection with refinancing of long-term debt					(190,000)		(204,000)
Payment of long-term debt					(3,470,000)	(7,718,000)	(3,514,000)
Extinguishment of debt					(8,864,000)
Net proceeds from issuance of common stock in connection with equity financings					1,233,000	81,525,000	15,694,000
Net proceeds from issuance of common stock through equity plans					743,000	1,218,000	351,000
Net cash provided by financing activities					14,452,000	75,025,000	12,327,000
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS					(73,291,000)	35,073,000	(27,408,000)
CASH, CASH EQUIVALENTS —Beginning of period		$ 87,975,000		$ 52,902,000	87,975,000	52,902,000	80,310,000
CASH, CASH EQUIVALENTS —End of period	$ 14,684,000		$ 87,975,000		14,684,000	87,975,000	52,902,000	$ 14,684,000
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Cash paid for interest					1,712,000	1,667,000	2,043,000
Income taxes (refunded) paid					(350,000)	2,000	2,000
NONCASH INVESTING AND FINANCING ACTIVITIES:
Purchases of property and equipment in accounts payable						410,000	222,000
Leasehold paid with note payable					899,000
Transfer of tenant improvement allowance to sublease					242,000
Establishment of right-of-use asset due to the adoption of ASU 2016-02					$ 4,730,000