Condensed Consolidated Statements of Stockholders' Equity - USD ($)	Total	Preferred Stock	Common Stock	Stock Subscription Receivable	Additional Paid-in Capital	Accumulated Deficit	Healios	Healios Common Stock	Healios Stock Subscription Receivable	Healios Additional Paid-in Capital
Preferred stock shares, beginning balance (in shares) at Dec. 31, 2018		0
Common stock, beginning balance (in shares) at Dec. 31, 2018			144,292,739
Beginning balance at Dec. 31, 2018	$ 43,116,000	$ 0	$ 144,000		$ 416,014,000	$ (373,042,000)
Stock-based compensation	1,090,000				1,090,000
Issuance of common stock (in shares)			3,825,000
Issuance of common stock	5,607,000		$ 4,000		5,603,000
Issuance of common stock under equity compensation plan (in shares)			158,494
Issuance of common stock under equity compensation plan	(69,000)				(69,000)
Net comprehensive income (loss)	(12,956,000)					(12,956,000)
Preferred stock shares, ending balance (in shares) at Mar. 31, 2019		0
Common stock, ending balance (in shares) at Mar. 31, 2019			148,276,233
Ending balance at Mar. 31, 2019	$ 36,788,000	$ 0	$ 148,000		422,638,000	(385,998,000)
Preferred stock shares, beginning balance (in shares) at Dec. 31, 2019	0	0
Common stock, beginning balance (in shares) at Dec. 31, 2019	159,791,585		159,791,585
Beginning balance at Dec. 31, 2019	$ 23,271,000	$ 0	$ 160,000	$ 0	440,735,000	(417,624,000)
Stock-based compensation	1,280,000				1,280,000
Stock subscription receivable from Healios warrant exercise (in shares)								4,000,000
Stock subscription receivable from Healios warrant exercise							$ 0	$ 4,000	$ (7,040,000)	$ 7,036,000
Issuance of common stock (in shares)			6,825,000
Issuance of common stock	10,250,000		$ 7,000		10,243,000
Issuance of common stock under equity compensation plan (in shares)			153,504
Issuance of common stock under equity compensation plan	(149,000)				(149,000)
Net comprehensive income (loss)	$ (15,644,000)					(15,644,000)
Preferred stock shares, ending balance (in shares) at Mar. 31, 2020	0	0
Common stock, ending balance (in shares) at Mar. 31, 2020	170,770,089		170,770,089
Ending balance at Mar. 31, 2020	$ 19,008,000	$ 0	$ 171,000	$ (7,040,000)	$ 459,145,000	$ (433,268,000)