Cash, Cash Equivalents, and Marketable Securities - Schedule of Unrealized Positions for Held-to-Maturity Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025
Marketable Securities [Line Items]
U.S. Treasury securities, available-for-sale, Amortized Cost	$ 2,876,156
U.S. Treasury securities, available-for-sale, Gross Unrealized Gains	538
U.S. Treasury securities, available-for-sale, Gross Unrealized Losses	(4,093)
U.S. Treasury securities, available-for-sale, Fair Value	2,872,601	$ 2,171,480
Accrued interest receivable	19,600	12,100
Corporate bonds
Marketable Securities [Line Items]
U.S. Treasury securities, available-for-sale, Amortized Cost	751,103
U.S. Treasury securities, available-for-sale, Gross Unrealized Gains	0
U.S. Treasury securities, available-for-sale, Gross Unrealized Losses	(2,681)
U.S. Treasury securities, available-for-sale, Fair Value	748,422	0
U.S. Treasury securities
Marketable Securities [Line Items]
U.S. Treasury securities, available-for-sale, Amortized Cost	2,125,053
U.S. Treasury securities, available-for-sale, Gross Unrealized Gains	538
U.S. Treasury securities, available-for-sale, Gross Unrealized Losses	(1,412)
U.S. Treasury securities, available-for-sale, Fair Value	2,124,179	0
U.S. Treasury securities, held-to-maturity, Amortized Cost		2,171,480
U.S. Treasury securities, held-to-maturity, Gross Unrealized Gains		1,267
U.S. Treasury securities, held-to-maturity, Gross Unrealized Losses		(463)
U.S. Treasury securities, held-to-maturity, Fair Value		$ 2,172,284
129 Available-for-Sale Marketable Securities
Marketable Securities [Line Items]
U.S. Treasury securities, available-for-sale, Fair Value	$ 1,999,600

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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