Goodwill and Intangible Assets
 9 Months Ended
Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]  
Goodwill and Intangible Assets
Goodwill and Intangible Assets

Goodwill

Changes in the carrying amount of our goodwill are as follows (dollars in millions):
 
Goodwill
Balance at December 31, 2015
$
544.0

Acquisition (a)
148.1

Balance at September 30, 2016
$
692.1


___________
(a)
In connection with the August 2016 acquisition of TimBar Corporation (TimBar), the Company recorded $148.1 million of goodwill in the Packaging segment.

Goodwill represents the excess of the cost of an acquired business over the fair value of the identifiable tangible and intangible assets acquired and liabilities assumed in a business combination. At September 30, 2016 and December 31, 2015 we had $636.9 million and $488.8 million of goodwill recorded in our Packaging segment, respectively. At both September 30, 2016 and December 31, 2015 we had $55.2 million of goodwill recorded in our Paper segment.

Intangible Assets

Intangible assets are primarily comprised of customer relationships and trademarks and trade names.

The weighted average remaining useful life, gross carrying amount, and accumulated amortization of our intangible assets were as follows (dollars in millions):
 
September 30, 2016
 
December 31, 2015
 
Weighted Average Remaining Useful Life (in Years)
 
Gross 
Carrying
Amount
 
Accumulated
Amortization
 
Weighted Average Remaining Useful Life (in Years)
 
Gross 
Carrying
Amount
 
Accumulated
Amortization
Customer relationships (b)
13.3
 
$
408.0

 
$
73.2

 
13.3
 
$
311.5

 
$
57.3

Trademarks and trade names (b)
11.7
 
25.6

 
6.9

 
13.6
 
21.8

 
5.2

Other (b)
2.9
 
1.5

 
0.2

 
1.2
 
0.2

 
0.2

Total intangible assets (excluding goodwill)
13.2
 
$
435.1

 
$
80.3

 
13.6
 
$
333.5

 
$
62.7



___________
(b)
In connection with the August 2016 acquisition of TimBar, the Company recorded intangible assets of $96.5 million for customer relationships, $3.8 million for trade names, and $1.3 million for other intangibles.

During the three months ended September 30, 2016 and 2015, amortization expense was $6.3 million and $5.7 million, respectively. During the nine months ended September 30, 2016 and 2015, amortization expense was $17.5 million and $17.1 million, respectively.