Fair Value Measurements - Summary of Financial Assets Recognized at Fair Value on Recurring Basis (Detail) - Fair Value on Recurring Basis [Member] - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets
Cash equivalents and restricted cash equivalents	$ 138,269	$ 124,636
Marketable securities:
Marketable securities	861,355	962,643
Total Assets	999,624	1,087,279
Liabilities
Liabilities measured at fair value	10,962
U.S. Treasury and Other Government Securities [Member]
Marketable securities:
Marketable securities	292,473	300,477
Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	378,507	440,416
Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	52,175	62,349
Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	138,200	159,401
Level 1 [Member]
Assets
Cash equivalents and restricted cash equivalents	138,269	124,636
Marketable securities:
Marketable securities	277,345	280,085
Total Assets	415,614	404,721
Level 1 [Member] | U.S. Treasury and Other Government Securities [Member]
Marketable securities:
Marketable securities	277,345
Total Assets		280,085
Level 2 [Member]
Marketable securities:
Marketable securities	584,010	682,558
Total Assets	584,010	682,558
Level 2 [Member] | U.S. Treasury and Other Government Securities [Member]
Marketable securities:
Marketable securities	15,128	20,392
Level 2 [Member] | Financial Institution Debt Securities [Member]
Marketable securities:
Marketable securities	378,507	440,416
Level 2 [Member] | Corporate Debt Securities [Member]
Marketable securities:
Marketable securities	52,175	62,349
Level 2 [Member] | Other Asset Backed Securities [Member]
Marketable securities:
Marketable securities	138,200	$ 159,401
Level 3 [Member]
Liabilities
Liabilities measured at fair value	10,962
Level 3 [Member] | Contingent Consideration Liability - research [Member]
Liabilities
Liabilities measured at fair value	$ 10,962