Intangible Assets
 9 Months Ended
Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]  
Intangible Assets
Intangible Assets
Intangible assets consist of the following:
 
September 30, 2016
 
December 31, 2015
 
Gross Carrying Amount
 
Accumulated Amortization
 
Net
 
Remaining Useful Life (Years)
 
Gross Carrying Amount
 
Accumulated Amortization
 
Net
 
Remaining Useful Life (Years)
Customer relationships
$
11,731

 
$
(7,932
)
 
$
3,799

 
5.7
 
$
11,731

 
$
(6,865
)
 
$
4,866

 
6.0
Disposal permits
1,269

 
(572
)
 
697

 
4.4
 
1,269

 
(451
)
 
818

 
5.2
Customer contracts
17,352

 
(6,943
)
 
10,409

 
10.0
 
17,352

 
(6,169
)
 
11,183

 
11.0
 
$
30,352

 
$
(15,447
)
 
$
14,905

 
8.6
 
$
30,352

 
$
(13,485
)
 
$
16,867

 
9.3

The remaining weighted average useful lives shown are calculated based on the net book value and remaining amortization period of each respective intangible asset.