Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Details)

v3.10.0.1
Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Details)
 3 Months Ended 9 Months Ended
Sep. 30, 2018
USD ($)
shares
Sep. 30, 2017
USD ($)
Sep. 30, 2018
USD ($)
Award
shares
Sep. 30, 2017
USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock available for award under plans | shares 13,342,827   13,342,827  
Number of cash based awards | Award     2  
Recognized incentive compensation expense $ 1,374,000 $ 1,984,000 $ 3,808,000 $ 6,324,000
Directors Compensation Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common stock available for award under plans | shares 128,980   128,980  
Restricted Stock Units (RSUs)        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common shares available for issuance reduced conversion basis     One-for-one basis  
Aggregate fair value of shares at the grant dates     $ 100,000  
Aggregate fair value of shares at the vesting date     200,000  
Unrecognized share-based compensation expense $ 8,300,000   $ 8,300,000  
Recognition period for unrecognized compensation expense     2020-11  
Recognized incentive compensation expense 1,304,000 1,914,000 $ 3,598,000 6,114,000
Restricted Shares        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Aggregate fair value of shares at the grant dates     300,000  
Aggregate fair value of shares at the vesting date     700,000  
Unrecognized share-based compensation expense 400,000   $ 400,000  
Recognition period for unrecognized compensation expense     2021-04  
Recognized incentive compensation expense $ 70,000 $ 70,000 $ 210,000 $ 210,000
Restricted Shares | Directors Compensation Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Common shares available for issuance reduced conversion basis     One-to-one basis  
2018 Long-term Cash-based Awards        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Cash-based awards payment date     Dec. 14, 2020  
2018 Short-term Cash-based Awards        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Cash-based awards payment date     Mar. 15, 2019  
2018 Short-term Cash-based Awards | Minimum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Adjusted EBITDA less interest expense     $ 200,000,000  
2017 Cash-based Awards        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Cash based award expected payment period     2018-03  
2017 Cash-based Awards | Minimum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Adjusted EBITDA less interest expense     $ 200,000,000  
2016 Cash-based Awards        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Recognized incentive compensation expense     $ 0  
Cash based compensation payment period after achievement of financial condition     30 days  
2016 Cash-based Awards | Minimum        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Adjusted EBITDA less interest expense     $ 300,000,000