Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Asset:
Asset, fair value	$ 234,914	$ 374,911
Money Market Fund
Asset:
Asset, fair value	123,455	95,063
U.S. Treasury Shares
Asset:
Asset, fair value	3,112	23,219
Corporate Bonds
Asset:
Asset, fair value	47,387	83,587
Commercial Paper
Asset:
Asset, fair value	26,148	121,773
Repo Securities
Asset:
Asset, fair value	4,750	8,000
Asset Backed Securities
Asset:
Asset, fair value	4,498	8,816
Certificates of Deposit
Asset:
Asset, fair value	22,119	21,553
Non-US Government
Asset:
Asset, fair value	3,445	12,900
Level 1
Asset:
Asset, fair value	126,567	118,282
Level 1 | Money Market Fund
Asset:
Asset, fair value	123,455	95,063
Level 1 | U.S. Treasury Shares
Asset:
Asset, fair value	3,112	23,219
Level 2
Asset:
Asset, fair value	108,347	256,629
Level 2 | Corporate Bonds
Asset:
Asset, fair value	47,387	83,587
Level 2 | Commercial Paper
Asset:
Asset, fair value	26,148	121,773
Level 2 | Repo Securities
Asset:
Asset, fair value	4,750	8,000
Level 2 | Asset Backed Securities
Asset:
Asset, fair value	4,498	8,816
Level 2 | Certificates of Deposit
Asset:
Asset, fair value	22,119	21,553
Level 2 | Non-US Government
Asset:
Asset, fair value	$ 3,445	$ 12,900