4. GOODWILL AND INTANGIBLE ASSETS

Goodwill:

Goodwill by reporting unit as at December 31, 2018 and December 31, 2017 was as follows:



	Bulgaria			Czech Republic			Romania			Slovak Republic		Slovenia			Total
Gross Balance, December 31, 2016	$	171,389		$	744,483		$	82,786		$	46,089	$	19,400		$	1,064,147
Accumulated impairment losses	(144,639		)	(287,545		)	(11,028		)	—		(19,400		)	(462,612		)
Balance, December 31, 2016	26,750			456,938			71,758			46,089		—			601,535
Foreign currency	3,682			93,249			7,519			6,374		—			110,824
Balance, December 31, 2017	30,432			550,187			79,277			52,463		—			712,359
Accumulated impairment losses	(144,639		)	(287,545		)	(11,028		)	—		(19,400		)	(462,612		)
Gross Balance, December 31, 2017	$	175,071		$	837,732		$	90,305		$	52,463	$	19,400		$	1,174,971



	Bulgaria			Czech Republic			Romania			Slovak Republic			Slovenia			Total
Gross Balance, December 31, 2017	$	175,071		$	837,732		$	90,305		$	52,463		$	19,400		1,174,971
Accumulated impairment losses	(144,639		)	(287,545		)	(11,028		)	—			(19,400		)	(462,612		)
Balance, December 31, 2017	30,432			550,187			79,277			52,463			—			712,359
Foreign currency	(1,377		)	(28,762		)	(3,505		)	(2,382		)	—			(36,026		)
Balance, December 31, 2018	29,055			521,425			75,772			50,081			—			676,333
Accumulated impairment losses	(144,639		)	(287,545		)	(11,028		)	—			(19,400		)	(462,612		)
Gross Balance, December 31, 2018	$	173,694		$	808,970		$	86,800		$	50,081		$	19,400		$	1,138,945

Other intangible assets:

Changes in the net book value of our other intangible assets as at December 31, 2018 and December 31, 2017 was as follows:



	December 31, 2018							December 31, 2017
	Gross		Accumulated Amortization			Net		Gross		Accumulated Amortization			Net
Indefinite-lived:
Trademarks	$	87,356	$	—		$	87,356	$	91,642	$	—		$	91,642
Amortized:
Broadcast licenses	210,447		(162,936		)	$	47,511	221,842		(163,468		)	58,374
Trademarks	631		(631		)	—		661		(661		)	—
Customer relationships	56,024		(55,158		)	$	866	58,771		(56,996		)	1,775
Other	1,868		(1,549		)	319		1,753		(1,567		)	186
Total	$	356,326	$	(220,274	)	$	136,052	$	374,669	$	(222,692	)	$	151,977

Broadcast licenses consist of our TV NOVA license in the Czech Republic, which is amortized on a straight-line basis through the expiration date of the license in 2025. Our customer relationships are deemed to have an economic useful life of, and are amortized on a straight-line basis, over five years to fifteen years.

The estimated amortization expense for the succeeding five years for our intangible assets with finite lives as of December 31, 2018 is as follows:



2019	$	8,374
2020	8,119
2021	8,051
2022	7,827
2023	7,827

Impairment of goodwill and other intangible assets:

Our annual assessment of impairment includes the allocation of corporate debt to individual reporting units based on their relative fair values. This allocation resulted in negative carrying values for the Romania, the Slovak Republic and Slovenia segments for the purpose of the assessment, however, none of these segments were determined to be impaired.

Upon conclusion of our annual impairment assessment, we determined that the fair value of our reporting units and other intangible assets were substantially in excess of their respective carrying values. We did not recognize any impairment charges in respect of goodwill and other intangible assets during the years ended December 31, 2018, 2017 or 2016. See Note 2, "Basis of Presentation and Summary of Significant Accounting Policies" for further information.