Intangibles, Net
 12 Months Ended
Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]  
Intangibles, Net
8.
Intangibles, Net
 
As of December 31, 2016
 
Remaining
Useful
Life (Years)
 
Gross
 
Accumulated
Amortization
 
Net
Customer relationships
2-14
 
$
36,265

 
$
14,396

 
$
21,869

Other
3-5
 
5,821

 
4,244

 
1,577

Intangible assets, net
 
 
$
42,086

 
$
18,640

 
$
23,446

 
As of December 31, 2015
 
Remaining
Useful
Life (Years)
 
Gross
 
Accumulated
Amortization
 
Net
Customer relationships
3-15
 
$
30,426

 
$
10,204

 
$
20,222

Other
4-6
 
5,121

 
3,230

 
1,891

Intangible assets, net
 
 
$
35,547

 
$
13,434

 
$
22,113



The Partnership recorded amortization expense related to intangible assets of $5.2 million, $4.4 million and $3.2 million during the years ended December 31, 2016, 2015 and 2014, respectively. The amortization of intangible assets is recorded in depreciation and amortization expense.
During the year ended December 31, 2016, the Partnership acquired intangible assets of $6.5 million (consisting of $5.8 million of customer relationships and $0.7 million of other intangibles). During the year ended December 31, 2014, the Partnership acquired intangible assets of $19.2 million (consisting of $18.2 million of customer relationships and $1.0 million of other intangibles). See Note 2.
The estimated future annual amortization expense of intangible assets for the years ending December 31, 2017, 2018, 2019, 2020 and 2021 is $4.5 million, $3.7 million, $3.2 million, $2.7 million and $2.3 million, respectively. As acquisitions and dispositions occur in the future, these amounts may vary.