6. INTANGIBLE ASSETS AND GOODWILL
The Company's intangible assets and related accumulated amortization as of December 31, 2013 and 2012 consisted of the following (in millions):
| December 31, 2013 | December 31, 2012 | ||||||||||||||||||||
| Accumulated | Accumulated | ||||||||||||||||||||
| Gross | Amortization | Net | Gross | Amortization | Net | ||||||||||||||||
| Intangible assets subject to | |||||||||||||||||||||
| amortization: | |||||||||||||||||||||
| Customer relationships | $ | 531 | $ | (167) | $ | 364 | $ | 530 | $ | (78) | $ | 452 | |||||||||
| Cable franchise renewals and | |||||||||||||||||||||
| access rights | 287 | (120) | 167 | 269 | (110) | 159 | |||||||||||||||
| Other | 38 | (17) | 21 | 41 | (11) | 30 | |||||||||||||||
| Total | $ | 856 | $ | (304) | $ | 552 | $ | 840 | $ | (199) | $ | 641 | |||||||||
| Intangible assets not subject to | |||||||||||||||||||||
| amortization: | |||||||||||||||||||||
| Cable franchise rights | $ | 26,934 | $ | (922) | $ | 26,012 | $ | 26,933 | $ | (922) | $ | 26,011 | |||||||||
The Company recorded amortization expense of $126 million in 2013, $110 million in 2012 and $33 million in 2011. Based on the remaining carrying value of intangible assets subject to amortization as of December 31, 2013, amortization expense is expected to be $124 million in 2014, $119 million in 2015, $116 million in 2016, $111 million in 2017 and $33 million in 2018. These amounts may vary as acquisitions and dispositions occur in the future.
Changes in the carrying value of the Company's goodwill from January 1 through December 31 are presented below (in millions):
| 2013 | 2012 | ||||||||||||||||||||
| Balance at beginning of year | $ | 2,889 | $ | 2,247 | |||||||||||||||||
| Acquisition of DukeNet | 310 | — | |||||||||||||||||||
| Acquisition of Insight | — | 638 | |||||||||||||||||||
| Other changes and adjustments | (3) | 4 | |||||||||||||||||||
| Balance at end of year(a) | $ | 3,196 | $ | 2,889 | |||||||||||||||||
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Annual Impairment Analysis
As of the Company's July 1, 2013 annual testing date and based on its qualitative assessment, the Company determined that it was not more likely than not that its cable franchise rights and goodwill were impaired and, therefore, the Company did not perform a quantitative assessment as part of its annual impairment testing. In making that determination, management identified and analyzed qualitative factors, including factors that would most significantly impact a DCF valuation of the fair values of the cable franchise rights and the fair value of the Company's reporting units. This process included a review of the Company's most recent long-range projections, analysis of operating results versus the prior year, changes in market values, changes in discount rates and changes in terminal growth rate assumptions.