Goodwill and Other Intangible Assets |
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Goodwill and Intangible Assets Disclosure [Abstract] | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Goodwill and other intangible assets | Goodwill and Other Intangible Assets For the years ended December 31, 2017 and 2016, the changes in the book value of goodwill by segment were as follows:
Our identifiable intangible assets primarily consist of acquired permits and leasehold agreements and franchise agreements which grant us the right to operate out-of-home structures in specified locations and the right to provide advertising space on railroad and municipal transit properties. Identifiable intangible assets are amortized on a straight-line basis over their estimated useful life, which is the respective life of the agreement that in some cases includes historical experience of renewals. Our identifiable intangible assets consist of the following:
All of our intangible assets, except goodwill, are subject to amortization. Amortization expense was $100.1 million in 2017, $115.3 million in 2016 and $115.4 million in 2015, which includes the amortization of direct lease acquisition costs of $40.0 million in 2017, $38.2 million in 2016 and $36.3 million in 2015. Direct lease acquisition costs are amortized on a straight-line basis over the related customer lease term, which generally ranges from four weeks to one year. We expect our aggregate annual amortization expense for intangible assets, before considering the impact of future direct lease acquisition costs, for each of the years 2018 through 2022, to be as follows:
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