Intangibles and Goodwill - Intangible Assets (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2020
Mar. 31, 2019
Dec. 31, 2019
Intangible assets:      
Goodwill $ 309,589   $ 309,589
Summary of amortizable intangible assets:      
Cost 179,418   179,418
Accumulated Amortization (84,474)   (81,656)
Net 94,944   97,762
Amortization expense 2,800 $ 3,200  
Estimated amortization expense for the next five years and thereafter:      
Remainder of 2020 8,155    
2020 10,362    
2021 10,005    
2022 9,501    
2023 8,897    
Thereafter 48,023    
Net 94,944   97,762
Customer relationships      
Summary of amortizable intangible assets:      
Cost 150,239   150,239
Accumulated Amortization (69,680)   (67,317)
Net $ 80,559   82,922
Weighted-average, useful life 14 years 9 months 18 days    
Estimated amortization expense for the next five years and thereafter:      
Net $ 80,559   82,922
Carrier relationships      
Summary of amortizable intangible assets:      
Cost 18,300   18,300
Accumulated Amortization (5,203)   (4,934)
Net $ 13,097   13,366
Weighted-average, useful life 17 years    
Estimated amortization expense for the next five years and thereafter:      
Net $ 13,097   13,366
Non-compete agreements      
Summary of amortizable intangible assets:      
Cost 5,239   5,239
Accumulated Amortization (3,952)   (3,765)
Net $ 1,287   1,474
Weighted-average, useful life 6 years 8 months 12 days    
Estimated amortization expense for the next five years and thereafter:      
Net $ 1,287   1,474
Trade names      
Summary of amortizable intangible assets:      
Cost 5,640   5,640
Accumulated Amortization (5,640)   (5,640)
Net $ 0   0
Weighted-average, useful life 4 years    
Estimated amortization expense for the next five years and thereafter:      
Net $ 0   $ 0