9.     CUSTOMER CONTRACTS 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 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, 2011 and $4.0 million as of December 31, 2010.

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:

Total amortization expense was approximately $22.4 million in 2011, $20.4 million in 2010 and $21.3 million in 2009. Included in the table above are non-amortizable, indefinite lived intangible assets of $14.4 at December 31, 2011 and 2010.

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