v3.8.0.1
Income Taxes - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Mar. 31, 2017
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Operating Loss Carryforwards [Line Items]        
TCJA, Provisional tax expense (benefit) offset by valuation allowance   $ 105,700,000    
TCJA, Provisional income tax expense (benefit)   0    
Foreign Earnings Repatriated   0    
Cumulative Foreign Deficits   41,200,000    
Income tax expense   $ (1,600,000) $ (700,000) $ (100,000)
Tax Credit Carryforward, Expiration Date   Jan. 01, 2020    
Tax credit carryforwards subject to expiration   $ 2,100,000    
Net operating losses and tax credit carryforwards, limitations on use, ownership changes   50.00%    
Net operating losses and tax credit carryforwards, limitations on use, ownership change period (years)   3 years    
Valuation allowance amount   $ 263,500,000 $ 193,400,000  
Share-based compensation, excess tax benefits $ 161,800,000      
Unrecognized tax benefits   0    
Undistributed Earnings of Foreign Subsidiaries   1,200,000    
Unrecognized deferred tax liability related to earnings of foreign operations   400,000    
Federal [Member]        
Operating Loss Carryforwards [Line Items]        
Operating Loss Carryforwards   $ 761,600,000    
Operating Loss Carryforwards, Expiration Dates   Jan. 01, 2020    
Deferred Tax Assets, Tax Credit Carryforwards, Research   $ 33,300,000    
California Franchise Tax Board [Member]        
Operating Loss Carryforwards [Line Items]        
Net Operating Loss Carryforwards Expiring In Year Thirteen and Thereafter   324,200,000    
State and Local Jurisdiction [Member]        
Operating Loss Carryforwards [Line Items]        
Operating Loss Carryforwards   $ 456,300,000    
Operating Loss Carryforwards, Expiration Dates   Jan. 01, 2018    
Deferred Tax Assets, Tax Credit Carryforwards, Research   $ 33,800,000    
State and Local Jurisdiction [Member]        
Operating Loss Carryforwards [Line Items]        
Net Operating Loss Carryforwards Expiring In 2020   $ 111,400,000