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 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:



December 31,	2017			2016
(in thousands)
Customer contracts	$	290,628		$	251,194
Less: Accumulated amortization	(137,759		)	(133,728		)
Customer contracts, net	$	152,869		$	117,466

The carrying amount of customer contracts in foreign countries was $29.8 million as of December 31, 2017 and $29.7 million as of December 31, 2016.

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:



At December 31,	2017			2016
(in thousands)
Other intangible assets	$	75,780		$	56,937
Less: Accumulated amortization	(14,232		)	(12,627		)
Other intangible assets, net	$	61,548		$	44,310

The carrying amount of other intangible assets in foreign countries was $3.5 million as of December 31, 2017 and $3.8 million as of December 31, 2016.

Included in the table above are trademarks and trade names of $35.0 million and $32.7 million at December 31, 2017 and 2016, respectively. Also included in the table above are non-amortizable, indefinite lived intangible assets of $32.2 million and $29.7 million at December 31, 2017 and 2016, respectively.

The carrying amount of customer contracts and other intangible assets, net were as follows:



December 31,	2017		2016
(in thousands)
Customer contracts, net	$	152,869	$	117,466
Other intangible assets, net	61,548		44,310
Customer contracts and other intangible assets, net	$	214,417	$	161,776

Total amortization expense was approximately $29.2 million in 2017, $26.2 million in 2016 and $25.2 million in 2015.

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)
2018	$	27,029
2019	24,052
2020	21,872
2021	20,431
2022	18,925