Accounting Policies - Modified Retrospective Effect - Consolidated Balance Sheet (Details) - USD ($)	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable - Healios	$ 262,000		$ 586,000
Deferred revenue - Healios	0		(250,000)
Accumulated deficit	(373,042,000)	$ (348,759,000)	(350,630,000)
Healios License Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable - Healios	1,108,000	183,000	153,000
Contractual right to consideration from Healios		1,436,000
Deferred revenue - Healios	(674,000)	0	(521,000)
Advance from Healios	(3,139,000)	(250,000)	(134,000)
Balances without Adoption of Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	(378,142,000)		(350,630,000)
Balances without Adoption of Topic 606 | Healios License Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable - Healios			153,000
Contractual right to consideration from Healios			0
Deferred revenue - Healios	(2,154,000)		(521,000)
Advance from Healios			$ (134,000)
Adjustments Due to Topic 606 | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	(5,100,000)	1,871,000
Adjustments Due to Topic 606 | ASU 2014-09 | Healios License Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable - Healios		30,000
Contractual right to consideration from Healios		1,436,000
Deferred revenue - Healios	$ 1,480,000	521,000
Advance from Healios		$ (116,000)