v3.25.3

Investments - Temporarily Impaired Investments (Details) $ in Thousands	Sep. 30, 2025 USD ($) Investment
Investments [Abstract]
Number of investments (in Investment) \| Investment	174
Less than 12 months of temporary impairment	$ 392,289
Less than 12 months of temporary impairment	(261)
More than 12 months of temporary impairment	119,526
More than 12 months of temporary impairment	(115)
Total temporary impairment	511,815
Total temporary impairment	$ (376)
Corporate Debt Securities [Member]
Investments [Abstract]
Number of investments (in Investment) \| Investment	105
Less than 12 months of temporary impairment	$ 179,031
Less than 12 months of temporary impairment	(127)
More than 12 months of temporary impairment	55,955
More than 12 months of temporary impairment	(63)
Total temporary impairment	234,986
Total temporary impairment	$ (190)
Debt Securities Issued by U.S. Government Agencies [Member]
Investments [Abstract]
Number of investments (in Investment) \| Investment	43
Less than 12 months of temporary impairment	$ 71,369
Less than 12 months of temporary impairment	(60)
More than 12 months of temporary impairment	17,286
More than 12 months of temporary impairment	(16)
Total temporary impairment	88,655
Total temporary impairment	$ (76)
Debt Securities Issued by the U.S. Treasury [Member]
Investments [Abstract]
Number of investments (in Investment) \| Investment	25
Less than 12 months of temporary impairment	$ 141,191
Less than 12 months of temporary impairment	(74)
More than 12 months of temporary impairment	46,285
More than 12 months of temporary impairment	(36)
Total temporary impairment	187,476
Total temporary impairment	$ (110)
Other Municipal Debt Securities [Member]
Investments [Abstract]
Number of investments (in Investment) \| Investment	1
Less than 12 months of temporary impairment	$ 698
Less than 12 months of temporary impairment	0
More than 12 months of temporary impairment	0
More than 12 months of temporary impairment	0
Total temporary impairment	698
Total temporary impairment	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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IONIS PHARMACEUTICALS INC 10-Q