Intangibles and Goodwill (Tables)
 6 Months Ended
Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]  
Summary of amortizable intangible assets
The following is a summary of amortizable intangible assets as of June 30, 2018 and December 31, 2017 (in thousands):
 
June 30, 2018
 
December 31, 2017
 
Cost
 
Accumulated Amortization
 
Net
 
Cost
 
Accumulated Amortization
 
Net
Customer relationships
$
145,139

 
$
(52,931
)
 
$
92,208

 
$
145,139

 
$
(48,058
)
 
$
97,081

Carrier relationships
18,300

 
(3,319
)
 
14,981

 
18,300

 
(2,781
)
 
15,519

Non-compete agreements
5,239

 
(2,609
)
 
2,630

 
5,239

 
(2,216
)
 
3,023

Trade names
5,640

 
(4,449
)
 
1,191

 
5,640

 
(3,779
)
 
1,861

 
$
174,318

 
$
(63,309
)
 
$
111,009

 
$
174,318

 
$
(56,834
)
 
$
117,484


Note: Amounts may not foot due to rounding.
Estimated amortization expense for the next five years and thereafter
The estimated amortization expense for the next five years and thereafter is as follows (in thousands):
Remainder of 2018
$
6,386

2019
11,471

2020
10,639

2021
10,025

2022
9,668

Thereafter
62,820

Total
$
111,009