Cash, Cash Equivalents and Investments (Details) - USD ($) $ in Thousands, shares in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2021
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	$ 1,054,585	$ 1,333,022
Gross Unrealized Gains	9,728	158
Gross Unrealized Losses	(537)	(12,641)
Fair Value	1,063,776	1,320,539
Cash and Cash Equivalents	403,870	598,545
Marketable Securities	99,720	77,940
Short-Term Investments	560,186	644,054
Debt securities, available-for-sale, unrealized Loss	531,500	420,400
Continuous unrealized loss position of available-for-sale investments, unrealized losses	25,200	138,800
Continuous unrealized loss position of available-for-sale investments, gross unrealized losses	100	300
Share Purchase Agreement with CLBT
Restricted Cash and Cash Equivalents Items [Line Items]
Marketable Securities			$ 90,000
Investment owned, shares held			9.0
Investment, type			Common Stock
Marketable securities, unrealized gain	21,800	38,700
Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	720,595	700,337
Gross Unrealized Gains	9,721	150
Gross Unrealized Losses	(518)	(12,471)
Fair Value	729,798	688,016
Cash and Cash Equivalents	183,361	191,802
Marketable Securities	99,720	77,940
Short-Term Investments	446,717	418,274
Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	223,481	225,942
Gross Unrealized Gains	7	8
Gross Unrealized Losses	(19)	(170)
Fair Value	223,469	225,780
Cash and Cash Equivalents	110,000
Short-Term Investments	113,469	225,780
Cash
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	110,509	406,743
Fair Value	110,509	406,743
Cash and Cash Equivalents	110,509	406,743
Money market funds | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	101,721	1,470
Fair Value	101,721	1,470
Cash and Cash Equivalents	101,721	1,470
Agency bonds | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	87,635	222,057
Gross Unrealized Gains		2
Gross Unrealized Losses	(48)	(174)
Fair Value	87,587	221,885
Cash and Cash Equivalents	81,640	101,635
Short-Term Investments	5,947	120,250
Treasury bills | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	310,446
Gross Unrealized Gains	1
Gross Unrealized Losses	(441)
Fair Value	310,006
Short-Term Investments	310,006
U.S. Government
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	130,793
Gross Unrealized Losses	(29)
Fair Value	130,764
Short-Term Investments	130,764
Marketable securities | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	90,000	90,000
Gross Unrealized Gains	9,720
Gross Unrealized Losses		(12,060)
Fair Value	99,720	77,940
Marketable Securities	99,720	77,940
Corporate bonds | Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost		80,646
Gross Unrealized Gains		8
Gross Unrealized Losses		(165)
Fair Value		80,489
Short-Term Investments		80,489
Treasury bills | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost		148,063
Gross Unrealized Gains		28
Fair Value		148,091
Cash and Cash Equivalents		88,697
Short-Term Investments		59,394
Term deposits | Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	211,729	128,205
Fair Value	211,729	128,205
Cash and Cash Equivalents	110,000
Short-Term Investments	101,729	128,205
Corporate bonds | Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost	11,752
Gross Unrealized Gains	7
Gross Unrealized Losses	(19)
Fair Value	11,740
Short-Term Investments	$ 11,740
Commercial paper | Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost		14,456
Fair Value		14,456
Short-Term Investments		14,456
U.S. Government | Fair Value, Inputs, Level 1
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost		238,747
Gross Unrealized Gains		120
Gross Unrealized Losses		(237)
Fair Value		238,630
Short-Term Investments		238,630
Treasury Inflation-Protected Securities | Fair Value, Inputs, Level 2
Restricted Cash and Cash Equivalents Items [Line Items]
Amortized Cost		2,635
Gross Unrealized Losses		(5)
Fair Value		2,630
Short-Term Investments		$ 2,630