Revenue - Summary of Disaggregation of Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation Of Revenue [Line Items]
Total revenues	$ 136	$ 139
North America
Disaggregation Of Revenue [Line Items]
Total revenues	59	58
Latin America
Disaggregation Of Revenue [Line Items]
Total revenues	42	55
Europe, Middle East, and Africa
Disaggregation Of Revenue [Line Items]
Total revenues	31	23
Asia-Pacific
Disaggregation Of Revenue [Line Items]
Total revenues	$ 4	$ 3

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Ultragenyx Pharmaceutical Inc. 10-Q