Major Customers, Partnerships and Strategic Alliances - California Institute for Regenerative Medicine - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	May 31, 2014	Mar. 31, 2017	Mar. 31, 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research grants		$ 119,000	$ 231,000
California Institute for Regenerative Medicine [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Funds due under the agreement	$ 5,600,000
Agreement to receive	4 years
Research grants		0	0
Collaboration agreement related costs and expenses		$ 200,000	$ 300,000