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Stock-Based Compensation - Narrative (Detail)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2015
USD ($)
vesting_type
Sep. 30, 2014
USD ($)
Sep. 30, 2015
USD ($)
vesting_type
yr
shares
Sep. 30, 2014
USD ($)
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Number of award vesting types | vesting_type 3   3  
Cash Liability for Performance-Based Units | $ $ 0.0   $ 0.0  
Performance Shares [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ 0.0 $ 0.0 $ 0.0 $ 0.1
Stock-based compensation, maximum number of unvested shares     453,000  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares       7,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period     8,000 16,000
Market Based Awards [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $   0.0   $ 0.0
Stock-based compensation, maximum number of unvested shares     136,000  
Vesting period     8 years  
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares       22,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period     91,000 107,000
Service Based Award [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ 0.1 0.1 $ 0.2 $ 0.3
Vesting period     4 years  
Expiration period     8 years  
Options issued     21,000 5,000
Deferred Stock Units [Member]        
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 [Member] | Director [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares issued to non-employee individual     41,000 45,000
Deferred stock units, performance-based stock units and restricted stock [Member]        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Stock-based compensation expense | $ $ 0.1 $ 0.1 $ 1.0 $ 1.2
Vesting period     4 years