Significant Accounting Policies - Estimated Fair Value of Assets and Liability (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Asset:
Asset, fair value	$ 314,574	$ 374,911
Level 1
Asset:
Asset, fair value	136,250	118,282
Level 2
Asset:
Asset, fair value	178,324	256,629
Money Market Fund
Asset:
Asset, fair value	129,031	95,063
Money Market Fund | Level 1
Asset:
Asset, fair value	129,031	95,063
U.S. Treasury Shares
Asset:
Asset, fair value	7,219	23,219
U.S. Treasury Shares | Level 1
Asset:
Asset, fair value	7,219	23,219
Corporate Bonds
Asset:
Asset, fair value	59,944	83,587
Corporate Bonds | Level 2
Asset:
Asset, fair value	59,944	83,587
Commercial Paper
Asset:
Asset, fair value	73,652	121,773
Commercial Paper | Level 2
Asset:
Asset, fair value	73,652	121,773
Repo Securities
Asset:
Asset, fair value	4,750	8,000
Repo Securities | Level 2
Asset:
Asset, fair value	4,750	8,000
Asset Backed Securities
Asset:
Asset, fair value	6,707	8,816
Asset Backed Securities | Level 2
Asset:
Asset, fair value	6,707	8,816
Certificate of Deposit
Asset:
Asset, fair value	24,603	21,553
Certificate of Deposit | Level 2
Asset:
Asset, fair value	24,603	21,553
Non-US Government
Asset:
Asset, fair value	8,668	12,900
Non-US Government | Level 2
Asset:
Asset, fair value	$ 8,668	$ 12,900