Revenues - Summary of Transaction Price and Allocation of Transaction Price to the Performance Obligations (Details) - USD ($) $ in Millions	Dec. 31, 2025	Jun. 30, 2025
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price		$ 256
Taiho Pharmaceutical Co., Ltd
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price	$ 15
License and development services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price		192
License \| Taiho Pharmaceutical Co., Ltd
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price	7
Development services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price		17
R&D services \| Taiho Pharmaceutical Co., Ltd
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price	$ 8
Access right and option continuation periods
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price		30
Rights to certain studies
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total transaction price		$ 17