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 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 8 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 $6.3 million as of December 31, 2013 and $5.4 million as of December 31, 2012.

Other intangible assets include non-compete agreements, patents and finite lived and indefinite lived trade names. 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 $0.4 million as of December 31, 2013 and $0.1 million as of December 31, 2012.

Included in the table above are trademarks and tradenames of $14.8 million and $15.3 million at December 31, 2013 and 2012, respectively. Also included in the table above are non-amortizable, indefinite lived intangible assets $12.6 million at December 31, 2013 and 2012, respectively.

Total amortization expense was approximately $25.2 million in 2013, $23.4 million in 2012 and $22.4 million in 2011.

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:

(in thousands)