Goodwill and tradenames are not subject to amortization. As of December 31, 2018 and 2017, the carrying values were $1.4 billion for goodwill and $0.8 billion for tradenames. 

The gross carrying amounts of intangible assets included within other long-term assets, the related accumulated amortization, the net carrying amounts and the weighted-average amortization periods of the Company’s intangible assets are listed in the following tables (in thousands, except amortization period):

The aggregate amortization expense is as follows (in thousands):

The following table sets forth the Company’s estimated aggregate amortization expense for each of the five years below (in thousands):