CIRM Grants (Details) $ in Millions			12 Months Ended
	Apr. 01, 2021 USD ($)	Jan. 04, 2021 USD ($)	Dec. 31, 2019 USD ($) Grant	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Nov. 12, 2020 USD ($)	Apr. 30, 2019 USD ($)
LAD-I CIRM Grant [Member]
CIRM Grants [Abstract]
Grant award for clinical development support							$ 6.5
Number of grants | Grant			2
Amount received from grant for eligible costs incurred			$ 1.2
Grant receivable included in prepaid and other assets				$ 1.0	$ 1.1
Milestone payments received		$ 1.1
IMO CIRM Grant [Member]
CIRM Grants [Abstract]
Grant award for clinical development support						$ 3.7
Amount received from grant for eligible costs incurred		$ 1.1
Grant receivable included in prepaid and other assets				$ 0.1	$ 0.9
Subsequent Event [Member] | LAD-I CIRM Grant [Member]
CIRM Grants [Abstract]
Milestone payments received	$ 1.0