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Stock-Based Compensation - Narrative (Detail)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2016
USD ($)
vesting_type
Jun. 30, 2015
USD ($)
Jun. 30, 2016
USD ($)
vesting_type
yr
shares
Jun. 30, 2015
USD ($)
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of award vesting types | vesting_type 2   2  
Cash liability for performance-based units | $ $ 0.0   $ 0.0  
Performance Shares        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ 0.0 $ 0.0 $ 0.1 $ 0.0
Stock-based compensation, maximum number of unvested shares | shares     453,000  
Service Based Award        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ 0.0 0.1 $ 0.1 $ 0.2
Vesting period     4 years  
Expiration period     8 years  
Options issued | shares     11,000 21,000
Options, forfeitures in period | shares     8,000 6,000
Deferred Stock Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Percentage of shares vested in lieu of directors fees at the grant date     100.00%  
Portion of Director fees matched to deferred stock units     25.00%  
Vesting period of deferred stock     1 year  
Minimum age required for meeting directors fees deferred vest criteria | yr     65  
Deferred Stock Units | Director        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares issued to non-employee individual | shares     40,000 39,000
Deferred stock units, performance-based stock units and restricted stock        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ $ 0.5 $ 0.6 $ 1.1 $ 0.8