v3.20.4
Income Taxes - Additional Information (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Mar. 31, 2020
Dec. 31, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Apr. 30, 2020
Aug. 31, 2019
Income Taxes [Line Items]                
Income tax expense     $ 18,654 $ 393 $ 2,547      
Tax benefit (expense) computed at the federal statutory rate     21.00% 21.00% 21.00%      
Change in enacted tax rate, amount     $ 39,700          
Net deferred tax liability   $ 7 $ 7 $ 417        
Pre-Tax Act U.S. federal net operating loss carry-forwards beginning of expiration year     2031          
Pre-Tax Act U.S. state net operating loss carry-forwards beginning of expiration year     2026          
U.S. Federal research tax credits beginning of expiration year     2032          
Deferred tax assets, valuation allowance   2,293,361 $ 2,293,361 1,811,666        
Gross unrecognized tax benefits, including related interest and penalties   345,328 345,328 286,805        
Net unrecognized tax benefits   344,971 344,971 286,605 $ 251,808      
Amount of tax benefit when gross unrecognized tax benefits realized     12,300          
Other Liabilities                
Income Taxes [Line Items]                
Net unrecognized tax benefits   $ 11,800 11,800 $ 1,500        
Convertible Notes                
Income Taxes [Line Items]                
Net deferred tax liability             $ 69,900 $ 92,100
U.K.                
Income Taxes [Line Items]                
Tax benefit (expense) computed at the federal statutory rate 17.00% 19.00%            
Net operating loss carry-forwards   $ 2,100,000 $ 2,100,000          
Percentage of taxable income limitation     50.00%          
Income tax year under examination     2018          
Federal                
Income Taxes [Line Items]                
Net operating loss carry-forwards   5,300,000 $ 5,300,000          
Pre-Tax Act operating loss carry-forwards           $ 1,500,000    
Post-Tax Act operating loss carry-forwards   3,800,000 $ 3,800,000          
Pre-Tax Act operating loss carry-forwards period           20 years    
Percentage of taxable income limitation     80.00%          
Federal | Research                
Income Taxes [Line Items]                
Accumulated research tax credits   302,600 $ 302,600          
State                
Income Taxes [Line Items]                
Net operating loss carry-forwards   3,200,000 3,200,000          
State | Research                
Income Taxes [Line Items]                
Accumulated research tax credits   $ 190,400 $ 190,400