PROPERTY, PLANT AND EQUIPMENT, INTANGIBLE ASSETS AND GOODWILL

Property, Plant and Equipment

The Company’s property, plant and equipment consisted of the following classes of assets as of March 31, 2018 and December 31, 2017, respectively:



(In thousands)	March 31, 2018		December 31, 2017
Land, buildings and improvements	$	565,397	$	562,702
Structures	2,890,924		2,864,442
Towers, transmitters and studio equipment	357,149		356,664
Furniture and other equipment	727,825		707,163
Construction in progress	69,958		74,810
	4,611,253		4,565,781
Less: accumulated depreciation	2,772,454		2,681,067
Property, plant and equipment, net	$	1,838,799	$	1,884,714

Indefinite-lived Intangible Assets

The Company’s indefinite-lived intangible assets consist of Federal Communications Commission (“FCC”) broadcast licenses in its iHM segment and billboard permits in its Americas outdoor advertising segment. Due to significant differences in both business practices and regulations, billboards in the International outdoor segment are subject to long-term, finite contracts unlike the Company’s permits in the United States. Accordingly, there are no indefinite-lived intangible assets in the International outdoor segment.

Other Intangible Assets

Other intangible assets include definite-lived intangible assets and permanent easements. The Company’s definite-lived intangible assets primarily include transit and street furniture contracts, talent and representation contracts, customer and advertiser relationships, and site leases and other contractual rights, all of which are amortized over the shorter of either the respective lives of the agreements or over the period of time the assets are expected to contribute directly or indirectly to the Company’s future cash flows. Permanent easements are indefinite-lived intangible assets which include certain rights to use real property not owned by the Company. The Company periodically reviews the appropriateness of the amortization periods related to its definite-lived intangible assets. These assets are recorded at cost.

The following table presents the gross carrying amount and accumulated amortization for each major class of other intangible assets as of March 31, 2018 and December 31, 2017, respectively:



(In thousands)	March 31, 2018					December 31, 2017
	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Transit, street furniture and other outdoor contractual rights	$	557,381	$	(453,022	)	$	548,918	$	(440,284	)
Customer / advertiser relationships	1,226,328		(1,163,781		)	1,226,314		(1,133,251		)
Talent contracts	161,962		(142,513		)	161,962		(138,728		)
Representation contracts	77,507		(65,191		)	77,507		(62,753		)
Permanent easements	162,920		—			162,920		—
Other	373,864		(231,799		)	372,292		(224,841		)
Total	$	2,559,962	$	(2,056,306	)	$	2,549,913	$	(1,999,857	)

Total amortization expense related to definite-lived intangible assets for the three months ended March 31, 2018 and 2017 was $47.0 million and $49.1 million, respectively.

As acquisitions and dispositions occur in the future, amortization expense may vary. The following table presents the Company’s estimate of amortization expense for each of the five succeeding fiscal years for definite-lived intangible assets:



(In thousands)
2019	$	46,286
2020	39,433
2021	34,595
2022	29,354
2023	21,643

Goodwill

The following table presents the changes in the carrying amount of goodwill in each of the Company’s reportable segments:



(In thousands)	iHM			Americas Outdoor Advertising		International Outdoor Advertising			Other		Consolidated
Balance as of December 31, 2016	$	3,288,481		$	505,478	$	190,785		$	81,831	$	4,066,575
Impairment	—			—		(1,591		)	—		(1,591		)
Acquisitions	2,442			2,252		—			—		4,694
Dispositions	(35,715		)	—		(1,817		)	—		(37,532		)
Foreign currency	—			—		18,847			—		18,847
Assets held for sale	—			89		—			—		89
Balance as of December 31, 2017	$	3,255,208		$	507,819	$	206,224		$	81,831	$	4,051,082
Dispositions	(1,606		)	—		—			—		(1,606		)
Foreign currency	—			—		4,624			—		4,624
Balance as of March 31, 2018	$	3,253,602		$	507,819	$	210,848		$	81,831	$	4,054,100