Note 4. Goodwill and Other Intangible Assets Components of other intangible assets  — Goodwill  — Our goodwill is assigned to our Off-Highway segment. Based on our October 31, 2014 impairment assessment,  the fair value of this segment is significantly higher than its carrying value, including goodwill.  We do not believe that our  goodwill is at risk of being impaired.  As discussed in Note 1 above, we adjusted goodwill in September 2014 in connection  with correcting an overstatement of our pension and postretirement obligations.The $3 adjustment is net of the cumulative  effect of currency fluctuations and impairment of the amount that would have been assigned at fresh start to our former  Driveshaft segment in 2008. The remaining change in the carrying amount of goodwill in 2014 is due to currency fluctuations. Non-amortizable intangible assets  — Our non-amortizable intangible assets include trademarks, trade names and intangible  assets used in research and development activities.  Trademarks and trade names consist of the Dana® and Spicer® trademarks  and trade names utilized in our Commercial  Vehicle and Off-Highway segments. We value trademarks and trade names using a  relief from royalty method which is based on revenue streams.  No impairment was recorded during the three years ended  December 31, 2014 in connection with the required annual assessment. Intangible assets used in research and development  activities relate to our strategic alliance with Fallbrook. See Note 2 for a discussion of our strategic alliance with Fallbrook and  our valuation of the related intangible assets used in research and development activities.  We value intangible assets used in  research and development activities using the multi-period excess earnings method, an income approach.No impairment was  recorded during the year ended December 31, 2014 in connection with the required annual assessment. Amortizable intangible assets  — Our amortizable intangible assets include core technology , customer relationships and a  portion of our trademarks and trade names. Core technology includes the proprietary know-how and expertise that is inherent in  our products and manufacturing processes. Customer relationships include the established relationships with our customers and  the related ability of these customers to continue to generate future recurring revenue and income. These assets are tested for impairment whenever events or changes in circumstances indicate that their carrying amounts  may not be recoverable. We group the assets and liabilities at the lowest level for which identifiable cash flows are lar gely  independent of the cash flows of other assets and liabilities and evaluate the asset group against the undiscounted future cash  flows. We use our internal forecasts, which we update quarterly , to develop our cash flow projections. These forecasts are based  on our knowledge of our customers’  production forecasts, our assessment of market growth rates, net new business, material  and labor cost estimates, cost recovery agreements with customers and our estimate of savings expected from our restructuring  activities. The most likely factors that would significantly impact our forecasts are changes in customer production levels and  loss of significant portions of our business. Our valuation is applied over the life of the primary assets within the asset groups.  If the undiscounted cash flows do not indicate that the carrying amount of the asset group is recoverable, an impairment char ge  is recorded if the carrying amount of the asset group exceeds its fair value based on discounted cash flow analyses or  appraisals. The net carrying amounts of intangible assets, other than goodwill, attributable to each of our operating segments at  December 31, 2014 were as follows: Light Vehicle Driveline (Light Vehicle) – $12, Commercial Vehicle – $94, Off-Highway –  $50 and Power Technologies – $13. December 31, 2014 December 31, 2013 Weighted Average Useful Life (years) Gross Carrying Amount Accumulated Impairment  and Amortization Net Carrying Amount Gross Carrying Amount Accumulated Impairment  and Amortization Net Carrying Amount Amortizable intangible assets Core technology 7 $ 90 $ (85) $ 5 $ 94 $ (83) $ 11 Trademarks and trade names 16 3 (1) 2 4 (1) 3 Customer relationships 8 493 (416) 77 527 (399) 128 Non-amortizable intangible assets Trademarks and trade names 65 65 65 65 Used in research and development activities 20 20 20 20 $ 671 $ (502) $ 169 $ 710 $ (483) $ 227 52