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Share-Based Compensation - Summary of Information about Restricted Stock Grants (Detail)
$ in Millions
12 Months Ended
Dec. 31, 2016
USD ($)
installment
shares
Dec. 31, 2015
shares
Dec. 31, 2014
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized Compensation | $ $ 4.2    
Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 571,000 818,000 577,000
Restricted Stock | October 2014      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 506,171    
Unrecognized Compensation | $ $ 0.6    
Remaining Period (in months) 10 months    
Number of vesting installments | installment 3    
Restricted Stock | April 2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 27,174    
Unrecognized Compensation | $ $ 0.1    
Remaining Period (in months) 10 months    
Number of vesting installments | installment 3    
Restricted Stock | October 2015      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 595,509    
Unrecognized Compensation | $ $ 1.0    
Remaining Period (in months) 22 months    
Number of vesting installments | installment 3    
Restricted Stock | January 2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 23,852    
Unrecognized Compensation | $ $ 0.0    
Remaining Period (in months) 22 months    
Number of vesting installments | installment 3    
Restricted Stock | March 2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 38,758    
Unrecognized Compensation | $ $ 0.0    
Remaining Period (in months) 22 months    
Number of vesting installments | installment 3    
Restricted Stock | October 2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 410,751    
Unrecognized Compensation | $ $ 2.1    
Remaining Period (in months) 34 months    
Number of vesting installments | installment 3    
Restricted Stock | October 2016      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Granted (in shares) | shares 97,951    
Unrecognized Compensation | $ $ 0.4    
Remaining Period (in months) 10 months