| Summary of Significant Classes of Amortizable Intangible Assets | 
 
 The following tables provide a summary of our significant classes
 of amortizable intangible assets: 
 
   
 
 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  | 
  
 
 |   | 
    | 
 As of December 31,
 2018 | 
   | 
  
 
 |   | 
    | 
 Cost | 
   | 
    | 
 Accumulated 
 Amortization | 
   | 
    | 
 Net | 
   | 
  
 
 |   | 
    | 
 (Dollars in
 thousands) | 
   | 
  
 
 | 
  
 Customer lists and contracts 
  | 
    | 
 $ | 
 24,673 | 
   | 
    | 
 $ | 
 (21,798 | 
 
)  | 
    | 
 $ | 
 2,875 | 
   | 
  
 
 | 
  
 Domain and brand names 
  | 
    | 
   | 
 21,358 | 
   | 
    | 
   | 
 (16,758 | 
 )  | 
    | 
   | 
 4,600 | 
   | 
  
 
 | 
  
 Favorable and assigned leases 
  | 
    | 
   | 
 2,256 | 
   | 
    | 
   | 
 (1,953 | 
 )  | 
    | 
   | 
 303 | 
   | 
  
 
 | 
  
 Subscriber base and lists 
  | 
    | 
   | 
 9,672 | 
   | 
    | 
   | 
 (7,198 | 
 )  | 
    | 
   | 
 2,474 | 
   | 
  
 
 | 
  
 Author relationships 
  | 
    | 
   | 
 2,771 | 
   | 
    | 
   | 
 (2,454 | 
 )  | 
    | 
   | 
 317 | 
   | 
  
 
 | 
  
 Non-compete agreements 
  | 
    | 
   | 
 2,048 | 
   | 
    | 
   | 
 (1,641 | 
 )  | 
    | 
   | 
 407 | 
   | 
  
 
 | 
  
 Other amortizable intangible assets 
  | 
    | 
   | 
 1,666 | 
   | 
    | 
   | 
 (1,378 | 
 )  | 
    | 
   | 
 288 | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
 
  | 
    | 
 $ | 
 64,444 | 
   | 
    | 
 $ | 
 (53,180 | 
 )  | 
    | 
 $ | 
 11,264 | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
 
 |   | 
    | 
 As of December 31,
 2017 | 
   | 
  
 
 |   | 
    | 
 Cost | 
   | 
    | 
 Accumulated 
 Amortization | 
   | 
    | 
 Net | 
   | 
  
 
 |   | 
    | 
 (Dollars in
 thousands) | 
   | 
  
 
 | 
  
 Customer lists and contracts 
  | 
    | 
 $ | 
 22,865 | 
   | 
    | 
 $ | 
 (20,888 | 
 )  | 
    | 
 $ | 
 1,977 | 
   | 
  
 
 | 
  
 Domain and brand names 
  | 
    | 
   | 
 20,109 | 
   | 
    | 
   | 
 (14,650 | 
 )  | 
    | 
   | 
 5,459 | 
   | 
  
 
 | 
  
 Favorable and assigned leases 
  | 
    | 
   | 
 2,379 | 
   | 
    | 
   | 
 (2,028 | 
 )  | 
    | 
   | 
 351 | 
   | 
  
 
 | 
  
 Subscriber base and lists 
  | 
    | 
   | 
 8,797 | 
   | 
    | 
   | 
 (4,701 | 
 )  | 
    | 
   | 
 4,096 | 
   | 
  
 
 | 
  
 Author relationships 
  | 
    | 
   | 
 2,771 | 
   | 
    | 
   | 
 (2,237 | 
 )  | 
    | 
   | 
 534 | 
   | 
  
 
 | 
  
 Non-compete agreements 
  | 
    | 
   | 
 2,029 | 
   | 
    | 
   | 
 (1,342 | 
 )  | 
    | 
   | 
 687 | 
   | 
  
 
 | 
  
 Other amortizable intangible assets 
  | 
    | 
   | 
 1,333 | 
   | 
    | 
   | 
 (1,333 | 
 )  | 
    | 
   | 
 
 —   | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
 
 |   | 
    | 
 $60,283 | 
   | 
    | 
 $(47,179) | 
   | 
    | 
 $13,104 | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
  
  
 | 
| Amortizable Intangible Assets, Estimate Amortization Expense | 
 
 Based on the amortizable intangible assets as of December 31,
 2018, we estimate amortization expense for the next five years to
 be as follows: 
 
   
 
 
  | 
  | 
  | 
  | 
  | 
  
 
 | 
  Year ended December 31, 
  | 
    | 
 
  Amortization Expense 
  | 
   | 
  
 
 |   | 
    | 
 (Dollars in
 thousands) | 
   | 
  
 
 | 
  2019 
  | 
    | 
 $ | 
 4,699 | 
   | 
  
 
 | 
  2020 
  | 
    | 
   | 
 3,275 | 
   | 
  
 
 | 
  2021 
  | 
    | 
   | 
 1,654 | 
   | 
  
 
 | 
  2022 
  | 
    | 
   | 
 969 | 
   | 
  
 
 | 
  2023 
  | 
    | 
   | 
 459 | 
   | 
  
 
 | 
  Thereafter 
  | 
    | 
   | 
 208 | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
 
 | 
  Total 
  | 
    | 
 $ | 
 11,264 | 
   | 
  
 
  | 
    | 
 
  
   
  | 
 
  
   
  | 
   | 
  
  
  
 |