INVESTMENTS - Summary of investments (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,355,348	$ 1,053,859
Unrealized Gains	425	2,543
Unrealized Losses	(3,015)	(1,260)
Fair Value	1,352,758	1,055,142
U.S. treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,034,662	802,288
Unrealized Gains	215	1,689
Unrealized Losses	(2,231)	(1,062)
Fair Value	1,032,646	802,915
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	281,821	234,908
Unrealized Gains	210	854
Unrealized Losses	(784)	(198)
Fair Value	281,247	235,564
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	38,865	16,663
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 38,865	$ 16,663