Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Amended Employee Agreement - Stephen Rizzone - Additional Information (Detail)

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Commitments and Contingencies - Amended Employee Agreement - Stephen Rizzone - Additional Information (Detail) - USD ($)
 12 Months Ended
May 21, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2013
Commitments And Contingencies [Line Items]          
Share-based compensation arrangement by share-based payment award, options, grants in period, gross   0 0 0  
Performance based equity plan market capitalization maximum amount       $ 1,100,000,000  
Performance based equity plan, market capitalization minimum amount       $ 100,000,000  
Performance Based Equity Plan [Member]          
Commitments And Contingencies [Line Items]          
Performance based equity plan market capitalization maximum amount $ 1,100,000,000        
Performance based equity plan, market capitalization minimum amount $ 100,000,000        
Percentage of performance share units to be earned on achievement of market capitalization growth 100.00% 100.00%   100.00%  
Percentage of performance share units to be paid on quarterly basis 50.00%        
Percentage of performance share units deferred 50.00%        
Percentage of performance share units to be paid on termination of employment agreement   25.00%      
Performance Share Units [Member] | Performance Based Equity Plan [Member]          
Commitments And Contingencies [Line Items]          
Share-based compensation arrangement by share-based payment award, options, grants in period, gross 639,075        
Second Employee Stock Option [Member]          
Commitments And Contingencies [Line Items]          
Deferred compensation arrangement with individual, exercise price         $ 6.00
Share-based compensation arrangement by share-based payment award, options, grants in period, gross         496,546
Employee Stock Option [Member]          
Commitments And Contingencies [Line Items]          
Deferred compensation arrangement with individual, maximum contractual term         48 months
Deferred compensation arrangement with individual, exercise price         $ 1.68
Share-based compensation arrangement by share-based payment award, options, grants in period, gross   0      
Mr. Rizzone [Member]          
Commitments And Contingencies [Line Items]          
Officers' compensation   $ 365,000      
Employment agreement percentage of base salary   100.00%      
Mr. Rizzone [Member] | Employee Stock Option [Member]          
Commitments And Contingencies [Line Items]          
Share-based compensation arrangement by share-based payment award, options, grants in period, gross         275,689