XML 77 R63.htm IDEA: XBRL DOCUMENT v3.8.0.1
Income Taxes - Additional Information (Detail) - USD ($)
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Operating Loss Carryforwards [Line Items]          
U.S. federal income tax rate     35.00%    
Additional income tax benefit due to decrease in federal corporate tax rate $ 23,000,000        
Deferred tax benefit due to remeasurement of certain deferred tax assets and liabilities 23,000,000        
Gross tax credits       $ (888,000) $ (2,846,000)
Federal net operating loss carryforward expiration year     2033    
State net operating loss carryforward expiration year     2017    
Excess income tax benefit associated with stock-based compensation in excess of par value       0 596,000
Excess income tax benefit associated with stock-based compensation recognized     $ 200,000    
Interest and penalties associated with unrecognized tax benefits     132,000 0 0
Accured interest and penalties associated with unrecognized tax benefits 201,000   201,000 0  
State and Local Jurisdiction [Member]          
Operating Loss Carryforwards [Line Items]          
State NOL carryforwards 0   0 400,000 9,600,000
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards 579,800,000   579,800,000    
Portion of state NOL carryforwards, not able to be utilized before expiration 536,000,000   536,000,000 312,300,000 $ 34,500,000
Valuation allowance for deferred assets associated with state NOL carryforwards 26,900,000   26,900,000 13,100,000  
Internal Revenue Service (IRS) [Member]          
Operating Loss Carryforwards [Line Items]          
Gross tax credits       $ 8,000,000  
Tax carryforward period       20 years  
Tax credit carryforward expiration year       2034  
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards $ 541,900,000   $ 541,900,000    
Scenario Forecast [Member]          
Operating Loss Carryforwards [Line Items]          
U.S. federal income tax rate   21.00%