Marketable Securities: Available-For-Sale Debt Securities - Schedule of Investments in Available-for-Sale Debt Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Aggregate estimated fair value	$ 196,578	$ 360,643
Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Aggregate estimated fair value	52,589	21,141
Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Aggregate estimated fair value	58,299	151,124
United Kingdom Government Securities
Debt Securities, Available-for-Sale [Line Items]
Aggregate estimated fair value	66,175	141,307
United States Treasury Bills
Debt Securities, Available-for-Sale [Line Items]
Aggregate estimated fair value	19,515	47,071
Debt Securities, Available-for-Sale
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	196,423	360,960
Gross unrealized gains	157	27
Gross unrealized losses	(2)	(344)
Aggregate estimated fair value	196,578	360,643
within 1 year \| Debt Securities, Available-for-Sale \| Commercial paper
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	52,569	21,145
Gross unrealized gains	21	3
Gross unrealized losses	(1)	(7)
Aggregate estimated fair value	52,589	21,141
within 1 year \| Debt Securities, Available-for-Sale \| Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	58,226	91,853
Gross unrealized gains	74	5
Gross unrealized losses	(1)	(70)
Aggregate estimated fair value	58,299	91,788
within 1 year \| Debt Securities, Available-for-Sale \| United Kingdom Government Securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	66,162	141,376
Gross unrealized gains	12	0
Gross unrealized losses	0	(69)
Aggregate estimated fair value	66,174	141,307
within 1 year \| Debt Securities, Available-for-Sale \| United States Treasury Bills
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	19,466	29,663
Gross unrealized gains	50	12
Gross unrealized losses	0	0
Aggregate estimated fair value	$ 19,516	29,675
1 to 5 years \| Debt Securities, Available-for-Sale \| Corporate debt securities
Debt Securities, Available-for-Sale [Line Items]
Amortized cost		59,530
Gross unrealized gains		0
Gross unrealized losses		(194)
Aggregate estimated fair value		59,336
1 to 5 years \| Debt Securities, Available-for-Sale \| United States Treasury Bills
Debt Securities, Available-for-Sale [Line Items]
Amortized cost		17,393
Gross unrealized gains		7
Gross unrealized losses		(4)
Aggregate estimated fair value		$ 17,396

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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