Goodwill and Other Intangible Assets

The carrying amount of goodwill, by operating segment is as follows:



(In thousands)	National Networks			International and Other			Total
December 31, 2016	$	242,303		$	415,405		$	657,708
Amortization of "second component" goodwill	(2,544		)	—			(2,544		)
Foreign currency translation	—			39,994			39,994
December 31, 2017	$	239,759		$	455,399		$	695,158
Additions	—			123,865			123,865
Amortization of "second component" goodwill	(1,328		)	—			(1,328		)
Foreign currency translation	—			(19,658		)	(19,658		)
December 31, 2018	$	238,431		$	559,606		$	798,037

The increase in the carrying amount of goodwill for the International and Other segment relates to the acquisitions of RLJE and Levity (see Note 7).

The reduction of $1.3 million in the carrying amount of goodwill for the National Networks is due to the realization of a tax benefit for the amortization of "second component" goodwill at SundanceTV. Second component goodwill is the amount of tax deductible goodwill in excess of goodwill for financial reporting purposes. In accordance with the authoritative guidance at the time of the SundanceTV acquisition, the tax benefits associated with this excess are applied to first reduce the amount of goodwill, and then other intangible assets for financial reporting purposes, if and when such tax benefits are realized in the Company's tax returns.

Annual Impairment Test of Goodwill

Based on the Company's annual impairment test for goodwill as of December 1, 2018, no impairment charge was required for any of the reporting units. The Company performed a qualitative assessment for all reporting units, with the exception of the International Programming Networks reporting unit. The qualitative assessments included, but were not limited to, consideration of the historical significant excesses of the estimated fair value of the reporting unit over its carrying value (including allocated goodwill), macroeconomic conditions, industry and market considerations, cost factors and historical and projected cash flows. The Company performed a quantitative assessment for the International Programming Networks reporting unit. Based on the quantitative assessment, if the fair value of the International Programming Networks reporting unit decreased by 6%, the Company would be required to record an impairment of goodwill.

In assessing the recoverability of goodwill for our International Programming Networks reporting unit, the Company must make assumptions regarding estimated future cash flows and other factors to determine the fair value of the reporting unit. Fair value estimates are made at a specific point in time, based on relevant information. These estimates are subjective in nature and involve uncertainties and matters of significant judgment. Estimates of fair value for goodwill impairment testing are primarily determined using discounted cash flows and comparable market transactions methods. The discounted cash flow method is based on estimates and assumptions of future revenue and expense and an appropriate discount rate. Projected future cash flows primarily include assumptions about renewals of affiliation agreements, the projected number of subscribers and the projected average rates per basic and viewing subscribers, trends in fixed price arrangements, the number of advertising spots and average rate per spot and the cost of program rights, among other assumptions. If these estimates or related assumptions change in the future, the Company may be required to record impairment charges related to goodwill. For example, if future revenue growth is lower than expected, or if programming costs exceed amounts currently expected, and the Company is unable to mitigate the impact of these factors, or if the discount rate used to estimate fair value increases 100 basis points or more, an impairment charge related to the goodwill associated with its International Programming Networks reporting unit may be required.

The following table summarizes information relating to the Company's identifiable intangible assets:



(In thousands)	December 31, 2018							Estimated Useful Lives
(In thousands)	Gross		Accumulated Amortization			Net		Estimated Useful Lives
Amortizable intangible assets:
Affiliate and customer relationships	$	620,771	$	(198,500	)	$	422,271	6 to 25 years
Advertiser relationships	46,282		(17,613		)	28,669		11 years
Trade names	118,772		(17,971		)	100,801		3 to 20 years
Other amortizable intangible assets	13,643		(6,377		)	7,266		5 to 15 years
Total amortizable intangible assets	799,468		(240,461		)	559,007
Indefinite-lived intangible assets:
Trademarks	19,900		—			19,900
Total intangible assets	$	819,368	$	(240,461	)	$	578,907
(In thousands)	December 31, 2017
(In thousands)	Gross		Accumulated Amortization			Net
Amortizable intangible assets:
Affiliate and customer relationships	$	527,713	$	(167,911	)	$	359,802
Advertiser relationships	46,282		(13,405		)	32,877
Trade names	53,761		(14,420		)	39,341
Other amortizable intangible assets	11,401		(6,079		)	5,322
Total amortizable intangible assets	639,157		(201,815		)	437,342
Indefinite-lived intangible assets:
Trademarks	19,900		—			19,900
Total intangible assets	$	659,057	$	(201,815	)	$	457,242

The increase in amortizable intangible assets relates to the acquisitions of RLJE and Levity (see Note 7).

Aggregate amortization expense for amortizable intangible assets for the years ended December 31, 2018, 2017 and 2016 was $43.0 million, $47.1 million and $38.6 million, respectively. Amortization expense in 2017 includes a $9.0 million charge from the accelerated amortization of certain identifiable intangible assets at AMCNI. Estimated aggregate amortization expense for intangible assets subject to amortization for each of the following five years is:



(In thousands)
Years Ending December 31,
2019	$	48,341
2020	48,184
2021	48,181
2022	47,558
2023	47,110

Impairment Test of Identifiable Indefinite-Lived Intangible Assets

Based on the Company's 2018 annual impairment test for identifiable indefinite-lived intangible assets, no impairment charge was required. The Company's indefinite-lived intangible assets relate to SundanceTV trademarks, which were valued using a relief-from-royalty method in which the expected benefits are valued by discounting estimated royalty revenue over projected revenues covered by the trademarks. In order to evaluate the sensitivity of the fair value calculations for the Company's identifiable indefinite-lived intangible assets, the Company applied a hypothetical 20% decrease to the estimated fair value of the identifiable indefinite-lived intangible assets. This hypothetical decrease in estimated fair value would not result in an impairment.

Significant judgments inherent in estimating the fair value of indefinite-lived intangible assets include the selection of appropriate discount and royalty rates, estimating the amount and timing of estimated future cash flows and identification of appropriate continuing growth rate assumptions. The discount rates used in the analysis are intended to reflect the risk inherent in the projected future cash flows generated by the respective intangible assets.