10.    CUSTOMER CONTRACTS, TRADENAMES AND TRADEMARKS, AND OTHER INTANGIBLE ASSETS

Customer contracts are amortized on a straight-line basis over the period of the agreements, as straight-line best approximates the ratio that current revenues bear to the total of current and anticipated revenues, based on the estimated lives of the assets. In accordance with the FASB ASC Topic 350 “Intangibles - Goodwill and other”, the expected lives of customer contracts were reviewed, and it was determined that customer contracts should be amortized over a life of 7 to 20 years dependent upon customer type. The carrying amount and accumulated amortization for customer contracts were as follows:

The carrying amount of customer contracts in foreign countries was $37.1 million as of December 31, 2018 and $29.8 million as of December 31, 2017.

Trademarks and tradenames are amortized on a straight-line basis over the period of its useful life. The Company has determined the assets have useful lives between 7 and 20 years with non-amortizable, indefinite lived Tradenames of $40.5 million and $30.0 million as of December 31, 2018 and 2017, respectively. The carrying amount and accumulated amortization for trademarks and tradenames were as follows:

The carrying amount of trademarks and tradenames in foreign countries was $3.7 million as of December 31, 2018 and $1.7 million as of December 31, 2017.

Other intangible assets include non-compete agreements and patents. Non-compete agreements are amortized on a straight-line basis over periods ranging from 3 to 20 years and patents are amortized on a straight-line basis over 15 years. The carrying amount and accumulated amortization for other intangible assets were as follows:

The carrying amount of other intangible assets in foreign countries was $1.6 million as of December 31, 2018 and $1.7 million as of December 31, 2017.

Included in the table above are non-amortizable, indefinite lived Internet domain names of $2.2 million at December 31, 2018 and 2017, respectively.

Total amortization expense was approximately $36.4 million in 2018, $29.2 million in 2017 and $26.2 million in 2016.

Estimated amortization expense for the existing carrying amount of customer contracts and other intangible assets for each of the five succeeding fiscal years are as follows: