INTANGIBLE ASSETS AND OTHER LONG-TERM ASSETS

Intangible Assets

Intangible assets are recorded at cost and are amortized on a straight-line basis over 10 to 47 years. Intangible assets consisted of the following:



	December 31, 2015					December 31, 2014
	Cost		Accumulated Amortization			Cost		Accumulated Amortization
	(Thousands of Dollars)
Customer relationships	$	196,616	$	(86,370	)	$	126,566	$	(69,711	)
Other	2,359		(594		)	2,359		(544		)
Total	$	198,975	$	(86,964	)	$	128,925	$	(70,255	)

All of our intangible assets are subject to amortization. Amortization expense for intangible assets was $16.7 million, $12.6 million and $13.8 million for the years ended December 31, 2015, 2014 and 2013, respectively. The estimated aggregate amortization expense is $13.8 million for the each of the years 2016 through 2020.

Other Long-Term Assets, Net

Other long-term assets, net consisted of the following:



	December 31,
	2015		2014
	(Thousands of Dollars)
Axeon Term Loan	$	170,352	$	169,235
Amount remaining in trust for the Gulf Opportunity Zone revenue bonds (Note 13)	54,822		72,240
Ammonia pipeline linefill and tank heel inventory	35,178		35,686
Deferred financing costs	29,939		32,957
Other	30,043		4,048
Other long-term assets, net	$	320,334	$	314,166

As of December 31, 2015, the carrying amount of the Axeon Term Loan is $170.4 million, consisting of the following: (i) the outstanding principal amount from the Axeon Term Loan of $190.0 million; (ii) plus the fair value of guarantees of $1.7 million; and (iii) less equity losses from our investment in Axeon of $21.3 million incurred prior to the 2014 Asphalt Sale and after the carrying value of our equity investment in Axeon was reduced to zero. We recognize interest income associated with the Axeon Term Loan ratably over the term of the loan in “Interest income, net” on the consolidated statements of income.

We provide credit support, such as guarantees, letters of credit and cash collateral, as applicable, of up to $150.0 million to Axeon, until February 26, 2016, at which point the amount of credit support will decrease by $25.0 million. Our obligation will continue to decrease until the obligation is terminated no later than September 28, 2019. In the event that we are obligated to perform under any of these guarantees or letters of credit, that amount paid by us will be treated as additional borrowings under the Axeon Term Loan. As a result, we adjust the carrying value of the Axeon Term Loan by the same amount as the liability for the fair value of the guarantees outstanding. As of December 31, 2015, we have provided $36.2 million in letters of credit on behalf of Axeon. Please refer to Note 16 for a discussion of the guarantees.

We review the financial information of Axeon monthly for possible credit loss indicators. Any repayments of the Axeon Term Loan, including those that were scheduled in 2014 and 2015, are subject to Axeon meeting certain restrictive requirements contained in its third-party asset-based revolving credit facility. In 2015 and 2014, Axeon failed to make two scheduled principal payments, increasing the interest rate payable by Axeon until Axeon makes the payments. While the Axeon Term Loan does not provide for any other scheduled payments, Axeon is required to use all of its excess cash, as defined in the Axeon Term Loan, to repay the Axeon Term Loan. The Axeon Term Loan must be repaid in full no later than September 28, 2019.