Discontinued Operations - Summary of Discontinued Operations Reported in Statement of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Total revenues		$ 1,180
Operating expenses:
Cost of product revenues		836
Research and development		130
Selling, general and administrative		9
Total costs and expenses		975
Net income from discontinued operations		$ 205
Net income per share
Basic and diluted		$ 0.00
Weighted-average shares used in computing net income per share basic and diluted
Basic and diluted	217,537	195,745
Product Revenue, Net [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Total revenues		$ 1,180