CROWN CASTLE INTERNATIONAL CORP | 2013 | FY | 3

Intangible Assets
Goodwill
The changes in the carrying value of goodwill for the year ended December 31, 2013 were as follows:
Balance as of December 31, 2011
$
2,035,390

Additions due to NextG Acquisition(a)
573,617

Additions due to WCP Acquisition (b)
54,824

Additions due to T-Mobile Acquisition (c)
428,019

Additions due to other acquisitions
28,113

Effect of exchange rate fluctuations
(6
)
Balance as of December 31, 2012
$
3,119,957

Additions due to AT&T Acquisition (c)
1,768,535

Additions due to other acquisitions
25,194

Effect of exchange rate fluctuations and other adjustments
2,740

Balance as of December 31, 2013
$
4,916,426

    
(a)
The purchase price allocation for the NextG Acquisition resulted in the recognition of a substantial amount of goodwill at CCUSA relative to the purchase price based on the following:
•
the acquired or in-process DAS have low average tenancy, which the Company believes provides an opportunity to co-locate additional tenants on those systems;
•
the Company believes that the economics associated with DAS are similar to the economics associated with the Company's towers, whereby expected increases in revenues from additional tenants on existing DAS are expected to result in high incremental margins due to relatively fixed operating costs;
•
the Company believes the demand for tenants to co-locate on DAS will be driven by the continued growth trends in the wireless communication industry as wireless carriers continue to focus on improving network quality and expanding capacity;
•
the Company believes the acquired DAS are well-positioned to benefit from the anticipated growth in the wireless industry with their previously mentioned locations in the ten largest metropolitan statistical areas in the U.S.; or
•
other intangibles not qualified for separate recognition, including the assembled work force.
To a lesser extent, a portion of the goodwill recognized is the result of recording the tax impact of the NextG Acquisition. See also note 10.
(b)
The Company paid a purchase price for the WCP Acquisition that resulted in goodwill at CCUSA primarily because of the strategic opportunities related to the acquired portfolio.
(c)
The purchase price allocation for the T-Mobile Acquisition and the preliminary purchase price allocation for the AT&T Acquisition resulted in the recognition of goodwill at CCUSA primarily because of the anticipated growth opportunities in the respective tower portfolios.
Intangibles
The following is a summary of the Company's intangible assets. See note 3 for further discussion of the Company's acquisitions.
 
As of December 31, 2013
 
As of December 31, 2012
 
Gross Carrying Value
 
Accumulated Amortization
 
Net Book Value
 
Gross Carrying Value
 
Accumulated Amortization
 
Net Book Value
Site rental contracts and customer relationships
$
4,761,605

 
$
(1,111,262
)
 
$
3,650,343

 
$
3,566,207

 
$
(913,647
)
 
$
2,652,560

Other intangible assets
486,751

 
(79,229
)
 
407,522

 
354,208

 
(65,072
)
 
289,136

Total
$
5,248,356

 
$
(1,190,491
)
 
$
4,057,865

 
$
3,920,415

 
$
(978,719
)
 
$
2,941,696


The components of the additions to intangible assets during the years ended December 31, 2013 and 2012 are as follows:
 
For Years Ended December 31,
 
2013
 
2012
 
Amount
 
Weighted-Average Amortization Period
 
Amount
 
Weighted-Average Amortization Period
 
 
 
(In years)
 
 
 
(In years)
Site rental contracts and customer relationships
$
1,203,596

 
20
 
$
741,526

 
21
Other intangible assets
132,763

(a) 
21
 
208,700

(b) 
19
Total
$
1,336,359

 
20
 
$
950,226

 
21
    
(a)
$114.9 million is related to below-market leases for land interests under acquired wireless infrastructure for the year ended December 31, 2013 which is inclusive of adjustments made during 2013 related to the T-Mobile purchase price allocation (see note 3).
(b)
$178.3 million is related to below-market leases for land interests under acquired wireless infrastructure for the year ended December 31, 2012.
Amortization expense related to intangible assets is classified as follows on the Company's consolidated statement of operations and comprehensive income (loss):
 
For Years Ended December 31,
Classification
2013
 
2012
 
2011
Depreciation, amortization and accretion
$
204,042

 
$
177,163

 
$
159,478

Site rental costs of operations
10,197

 
3,352

 
3,709

Total amortization expense
$
214,239

 
$
180,515

 
$
163,187


The estimated annual amortization expense related to intangible assets (inclusive of those recorded as an increase to "site rental costs of operations") for the years ended December 31, 2014 to 2018 is as follows:
 
Years Ending December 31,
 
2014

2015

2016

2017

2018
Estimated annual amortization
$
272,944

 
$
267,326

 
$
267,273

 
$
266,902

 
$
266,732

us-gaap:GoodwillAndIntangibleAssetsDisclosureTextBlock