Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Tax Credit Carryforward [Line Items]
Valuation allowance	$ 832,200	$ 1,013,700
Changes in valuation allowances	(190,200)
Total deferred charges and prepaid taxes	498,800	273,100
Unrecognized tax benefits	180,000	186,300	$ 173,400	$ 606,400
Increase (decrease) in unrecognized tax benefit			(450,000)
Unrecognized tax benefit	127,600	139,300	147,600
Net interest expense	12,600	13,800	5,100
Unrecognized tax benefits, interest on income taxes accrued	48,500	40,700
Neurimmune
Tax Credit Carryforward [Line Items]
Effective income tax rate reconciliation, disposition of business, amount			7,400
2017 Tax Act
Tax Credit Carryforward [Line Items]
Transition toll tax liabilities		234,000
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	356,600
Foreign Tax Jurisdiction
Tax Credit Carryforward [Line Items]
Valuation allowance	832,200	1,013,700	1,278,700	2,003,300
Unrecognized tax benefits				$ 450,000
Foreign Tax Jurisdiction | Swiss Federal Tax Administration (FTA)
Tax Credit Carryforward [Line Items]
Changes in valuation allowances	37,900	$ 56,800
Foreign Tax Jurisdiction | Neurimmune
Tax Credit Carryforward [Line Items]
Valuation allowance increase (decrease)			(470,300)
Foreign Tax Jurisdiction | Neurimmune | Swiss Federal Tax Administration (FTA)
Tax Credit Carryforward [Line Items]
Valuation allowance increase (decrease)			$ (230,300)
General Business | Domestic Country
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	146,200
Operating loss carryforwards	142,800
General Business | Foreign Tax Jurisdiction
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	9,100,000
Operating loss carryforwards	8,400,000
Research | State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	172,100
Minimum
Tax Credit Carryforward [Line Items]
Residual U.S. tax liability on reversal of deferred tax liabilities on foreign subsidiaries purchase accounting	300,000
Maximum
Tax Credit Carryforward [Line Items]
Residual U.S. tax liability on reversal of deferred tax liabilities on foreign subsidiaries purchase accounting	$ 400,000