Annual report pursuant to Section 13 and 15(d)

Stock-based and Long-Term Compensation - Narrative (Details)

v3.8.0.1
Stock-based and Long-Term Compensation - Narrative (Details) - USD ($)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock options granted (in shares) 0 0 0
Outstanding options, intrinsic value $ 0    
Exercisable options, intrinsic value $ 0    
Options outstanding, weighted average remaining contractual term 1 year 7 months 7 days    
Options exercisable, weighted average remaining contractual term 1 year 7 months 7 days    
Restricted Stock | Common Class B      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Outstanding restricted stock awards (in shares) 0    
Restricted Stock and Restricted Stock Units      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Compensation cost not yet recognized $ 2,264,000    
Compensation cost not yet recognized, period for recognition 2 years 9 months 18 days    
Phantom Units | 2017 Plan      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 3 years    
Granted (in shares) 45,812    
Accrued estimated vested value $ 202,000    
Phantom Units | 2017 Plan | Grant Date      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 33.00%    
Phantom Units | 2017 Plan | Year One Following Grant Date      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 33.00%    
Phantom Units | 2017 Plan | Year Two Following Grant Date      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting rights, percentage 33.00%    
Minimum | Employee Stock Option      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award expiration period 5 years    
Award vesting period 2 years    
Minimum | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 2 years    
Maximum | Employee Stock Option      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award expiration period 7 years    
Award vesting period 4 years    
Maximum | Restricted Stock      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Award vesting period 5 years