FAIR VALUE MEASUREMENTS - Fair Value of Assets Measured on a Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Financial assets
Cash equivalents	$ 34,159	$ 113,243
Marketable debt securities	1,649,675	1,411,133
Marketable equity securities	$ 11,178	$ 28,122
Financial liabilities
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other liabilities	Other liabilities
Recurring
Financial assets
Marketable equity securities	$ 11,178	$ 28,122
Total financial assets	1,828,122	1,710,846
Financial liabilities
Development derivative liability	324,941	209,277
Recurring | Money market funds
Financial assets
Cash equivalents	166,059	270,394
Restricted cash (money market funds)	1,210	1,197
Recurring | U.S. treasury securities
Financial assets
Cash equivalents	30,712	44,817
Marketable debt securities	862,022	820,913
Recurring | Commercial paper
Financial assets
Cash equivalents	2,685	22,350
Marketable debt securities	56,216	36,793
Recurring | Corporate notes
Financial assets
Cash equivalents	762	1,024
Marketable debt securities	252,350	208,284
Recurring | U.S. government-sponsored enterprise securities
Financial assets
Cash equivalents		41,763
Marketable debt securities	441,341	230,770
Recurring | Certificates of deposit
Financial assets
Cash equivalents		3,289
Marketable debt securities	3,587	1,130
Recurring | Quoted Prices in Active Markets (Level 1)
Financial assets
Marketable equity securities	11,178	28,122
Total financial assets	178,447	299,713
Financial liabilities
Development derivative liability	0	0
Recurring | Quoted Prices in Active Markets (Level 1) | Money market funds
Financial assets
Cash equivalents	166,059	270,394
Restricted cash (money market funds)	1,210	1,197
Recurring | Quoted Prices in Active Markets (Level 1) | U.S. treasury securities
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Quoted Prices in Active Markets (Level 1) | Commercial paper
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Quoted Prices in Active Markets (Level 1) | Corporate notes
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Quoted Prices in Active Markets (Level 1) | U.S. government-sponsored enterprise securities
Financial assets
Cash equivalents		0
Marketable debt securities	0	0
Recurring | Quoted Prices in Active Markets (Level 1) | Certificates of deposit
Financial assets
Cash equivalents		0
Marketable debt securities	0	0
Recurring | Significant Observable Inputs (Level 2)
Financial assets
Marketable equity securities	0	0
Total financial assets	1,649,675	1,411,133
Financial liabilities
Development derivative liability	0	0
Recurring | Significant Observable Inputs (Level 2) | Money market funds
Financial assets
Cash equivalents	0	0
Restricted cash (money market funds)	0	0
Recurring | Significant Observable Inputs (Level 2) | U.S. treasury securities
Financial assets
Cash equivalents	30,712	44,817
Marketable debt securities	862,022	820,913
Recurring | Significant Observable Inputs (Level 2) | Commercial paper
Financial assets
Cash equivalents	2,685	22,350
Marketable debt securities	56,216	36,793
Recurring | Significant Observable Inputs (Level 2) | Corporate notes
Financial assets
Cash equivalents	762	1,024
Marketable debt securities	252,350	208,284
Recurring | Significant Observable Inputs (Level 2) | U.S. government-sponsored enterprise securities
Financial assets
Cash equivalents		41,763
Marketable debt securities	441,341	230,770
Recurring | Significant Observable Inputs (Level 2) | Certificates of deposit
Financial assets
Cash equivalents		3,289
Marketable debt securities	3,587	1,130
Recurring | Significant Unobservable Inputs (Level 3)
Financial assets
Marketable equity securities	0	0
Total financial assets	0	0
Financial liabilities
Development derivative liability	324,941	209,277
Recurring | Significant Unobservable Inputs (Level 3) | Money market funds
Financial assets
Cash equivalents	0	0
Restricted cash (money market funds)	0	0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. treasury securities
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Commercial paper
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Corporate notes
Financial assets
Cash equivalents	0	0
Marketable debt securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | U.S. government-sponsored enterprise securities
Financial assets
Cash equivalents		0
Marketable debt securities	0	0
Recurring | Significant Unobservable Inputs (Level 3) | Certificates of deposit
Financial assets
Cash equivalents		0
Marketable debt securities	$ 0	$ 0