Business Overview, Basis of Presentation, and Recently Issued Accounting Standards (Details) $ / shares in Units, $ in Millions	Sep. 16, 2026 USD ($)	Aug. 01, 2026 USD ($) shares	Nov. 02, 2026 individual	Oct. 15, 2026 $ / shares	Sep. 30, 2026 $ / shares	Dec. 31, 2025 $ / shares
Business Combination [Line Items]
Common stock, par value (in dollars per share) \| $ / shares					$ 0.001	$ 0.50
Subsequent Event
Business Combination [Line Items]
Common stock, par value (in dollars per share) \| $ / shares				$ 0.001
Acquisition Term Loan \| Unsecured Debt
Business Combination [Line Items]
Commitments to extend credit		$ 650
Forecast
Business Combination [Line Items]
Number of Individuals on Board of Directors \| individual			8
Number of individuals on Board of Directors nominated by each company \| individual			4
Indivior Stockholders \| Forecast
Business Combination [Line Items]
Stockholders ownership percentage			56.50%
Supernus Stockholders \| Forecast
Business Combination [Line Items]
Stockholders ownership percentage			43.50%
Supernus Pharmaceuticals, Inc.
Business Combination [Line Items]
Share exchange ratio \| shares		1.5401
Termination fee		$ 174
Cash dividend	$ 1,000
Supernus Pharmaceuticals, Inc. \| Supernus Pharmaceuticals, Inc.
Business Combination [Line Items]
Termination fee		$ 101