Income taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Deferred tax assets:
Net operating loss carryforwards	$ 569,975	$ 524,598
Research tax credits	786,586	677,104
Reserves, accruals and other	27,463	33,312
Lease obligations	50,331	41,493
Share-based compensation	36,311	33,793
Research capitalization and amortization	486,379	623,368
Total deferred tax assets	1,957,045	1,933,668
Less: valuation allowance	(346,095)	(322,070)
Deferred tax assets, net of valuation allowance	1,610,950	1,611,598
Deferred tax liabilities:
Depreciation and amortization	(15,838)	(6,394)
Prepaid expenses	(2,959)	(2,665)
Total deferred tax liabilities	(18,797)	(9,059)
Deferred tax assets (liabilities)	$ 1,592,153	$ 1,602,539