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Equity Incentive Awards - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 6 Months Ended
May 01, 2018
Feb. 01, 2018
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
May 13, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Term of award (in years)         10 years    
Number of shares available for grant (in shares)     2,934,810   2,934,810    
Grants during the period (in shares) 6,270            
Maximum              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares authorized for issuance (in shares)             3,750,000
General and Administrative Expense              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation expense     $ 2.7 $ 2.5 $ 4.5 $ 4.3  
Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Equity instruments other than options, grants in period (in shares) 51,388 70,250          
Fair value of shares issued $ 4.6 $ 5.9          
Exercise price ( in usd per share) $ 89.65            
Management | Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Award vesting period (years)   3 years          
Management | Transition Award              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Equity instruments other than options, grants in period (in shares)   70,250          
Fair value of shares issued   $ 5.9          
Award vesting period (years)   3 years          
Vesting on December 28, 2018 | Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting rights (in percentage)         33.00%    
Vesting on December 28, 2018 | Transition Award              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting rights (in percentage)         67.00%    
Vesting on December 28, 2019 | Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting rights (in percentage)         33.00%    
Vesting on December 28, 2019 | Transition Award              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting rights (in percentage)         33.00%    
Vesting on December 28, 2020 | Restricted Stock              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Vesting rights (in percentage)         33.00%