Summary of Expiration of not Utilized Net Operating Loss and Tax Credit Carryforwards (Detail) $ in Thousands	Dec. 31, 2019 USD ($)
Federal
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 144,566
Federal R&D and orphan drug credit carryforwards	507,292
State
Income Tax Contingency [Line Items]
Net operating loss carryforwards	161,341
Federal R&D and orphan drug credit carryforwards	112,100
Dutch | Foreign
Income Tax Contingency [Line Items]
Net operating loss carryforwards	$ 89,064