Intangibles and Goodwill - Intangible Assets (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Dec. 31, 2019
Intangible assets:          
Goodwill $ 309,589   $ 309,589   $ 309,589
Summary of amortizable intangible assets:          
Cost 179,418   179,418   179,418
Accumulated Amortization (87,241)   (87,241)   (81,656)
Net 92,177   92,177   97,762
Amortization expense 2,800 $ 3,000 5,600 $ 6,200  
Estimated amortization expense for the next five years and thereafter:          
Remainder of 2020 5,389   5,389    
2020 10,362   10,362    
2021 10,005   10,005    
2022 9,501   9,501    
2023 8,897   8,897    
Thereafter 48,023   48,023    
Net 92,177   92,177   97,762
Customer relationships          
Summary of amortizable intangible assets:          
Cost 150,239   150,239   150,239
Accumulated Amortization (72,020)   (72,020)   (67,317)
Net 78,219   $ 78,219   82,922
Weighted-average, useful life     14 years 9 months 18 days    
Estimated amortization expense for the next five years and thereafter:          
Net 78,219   $ 78,219   82,922
Carrier relationships          
Summary of amortizable intangible assets:          
Cost 18,300   18,300   18,300
Accumulated Amortization (5,472)   (5,472)   (4,934)
Net 12,828   $ 12,828   13,366
Weighted-average, useful life     17 years    
Estimated amortization expense for the next five years and thereafter:          
Net 12,828   $ 12,828   13,366
Non-compete agreements          
Summary of amortizable intangible assets:          
Cost 5,239   5,239   5,239
Accumulated Amortization (4,109)   (4,109)   (3,765)
Net 1,130   $ 1,130   1,474
Weighted-average, useful life     6 years 8 months 12 days    
Estimated amortization expense for the next five years and thereafter:          
Net 1,130   $ 1,130   1,474
Trade names          
Summary of amortizable intangible assets:          
Cost 5,640   5,640   5,640
Accumulated Amortization (5,640)   (5,640)   (5,640)
Net 0   $ 0   0
Weighted-average, useful life     4 years    
Estimated amortization expense for the next five years and thereafter:          
Net $ 0   $ 0   $ 0