CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Statement of Comprehensive Income [Abstract]
Net loss	$ (180,413)	$ (133,516)	$ (446,444)	$ (435,798)
Other comprehensive income (loss):
Foreign currency translation adjustments	1,075	(1,481)	1,882	(1,571)
Unrealized gain (loss) on available-for-sale debt securities	13	3,472	(419)	1,820
Other comprehensive income:	1,088	1,991	1,463	249
Total comprehensive loss	$ (179,325)	$ (131,525)	$ (444,981)	$ (435,549)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

- Definition

Amount after tax, before reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

+ References + Details

- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

+ References

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+ Details

Ultragenyx Pharmaceutical Inc. 10-Q