Contract Manufacturing Agreement - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Aug. 31, 2017 USD ($) right $ / shares shares	Mar. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Long-term Purchase Commitment [Line Items]
Non-cash charge			$ 52,075	$ 56,406	$ 43,284
Lonza Manufacturing Services Agreement
Long-term Purchase Commitment [Line Items]
Term of manufacturing commitments	10 years
Lonza Manufacturing Services Agreement | Common Stock
Long-term Purchase Commitment [Line Items]
Number of separate rights to purchase shares of common stock | right	2
Follow on offering price per share | $ / shares	$ 1.00
Average trading period from date of purchase right	20 days
Lonza Manufacturing Services Agreement | Common Stock | Maximum
Long-term Purchase Commitment [Line Items]
Aggregate market value of shares to be purchased under each right	$ 15,000
Number of shares to be purchased under each right | shares	500,000
Non-employee stock | Lonza Manufacturing Services Agreement | Research and Development Expense
Long-term Purchase Commitment [Line Items]
Non-cash charge		$ 5,800
First Tranche | Lonza Manufacturing Services Agreement | Common Stock
Long-term Purchase Commitment [Line Items]
Transfer and exercised the right to purchase (in shares) | shares		500,000
Transfer and exercised the right to purchase price (in dollars per share) | $ / shares		$ 1.00