v3.26.1
Income Taxes - Additional Information (Detail) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Mar. 31, 2025
Mar. 31, 2026
Income Tax Contingency [Line Items]    
Capital loss carryforwards $ 252,589 $ 388,035
Valuation allowance 430,501 434,983
Valuation allowance, deferred tax asset, increase 10,300  
Impact on effective tax rate   13,600
Accrued interest or penalties associated with uncertain tax positions   5,500
Accrued interest income   7,100
Accrued interest and penalties $ 14,400 9,000
Tax benefit recognized for interest income in income tax expense   4,600
United Kingdom [Member]    
Income Tax Contingency [Line Items]    
Capital loss carryforwards   64,200
One Big Beautiful Bill Act [Member]    
Income Tax Contingency [Line Items]    
Valuation allowance, deferred tax asset, increase   10,700
United States [Member]    
Income Tax Contingency [Line Items]    
Operating loss carryforwards   $ 1,296,200
Operating loss carryforwards expiration beginning year   2029
Tax years subject to examination   2023 and thereafter
United States [Member] | Research & Development [Member]    
Income Tax Contingency [Line Items]    
Tax credit carryforward amount   $ 157,300
United States [Member] | Research & Development [Member] | Earliest Tax Year [Member]    
Income Tax Contingency [Line Items]    
Tax credit carryforwards expiration beginning year   2040
State [Member]    
Income Tax Contingency [Line Items]    
Operating loss carryforwards   $ 673,000
Operating loss carryforwards expiration beginning year   2027
Tax years subject to examination   2023 and thereafter
State [Member] | Research & Development [Member]    
Income Tax Contingency [Line Items]    
Tax credit carryforward amount   $ 217,600
State [Member] | Research & Development [Member] | Earliest Tax Year [Member]    
Income Tax Contingency [Line Items]    
Tax credit carryforwards expiration beginning year   2027
Foreign [Member]    
Income Tax Contingency [Line Items]    
Tax years subject to examination   2022 and thereafter