Acquired Intangible Assets and Liabilities

The following summarizes our acquired intangible assets (real estate intangibles, comprised of acquired in-place lease value and tenant relationship value along with acquired above-market lease value) and intangible liabilities (acquired below-market lease value) as of December 31, 2018 and 2017.



	Balance as of
(Amounts in thousands)	December 31, 2018			December 31, 2017

Acquired in-place lease value:
Gross amount	$	1,569,401		$	1,473,515
Accumulated amortization	(795,033		)	(613,948		)
Net	$	774,368		$	859,567
Tenant relationship value:
Gross amount	$	2,339,606		$	1,978,277
Accumulated amortization	(291,818		)	(169,919		)
Net	$	2,047,788		$	1,808,358
Acquired above-market leases:
Gross amount	$	277,796		$	294,514
Accumulated amortization	(158,037		)	(110,139		)
Net	$	119,759		$	184,375
Acquired below-market leases:
Gross amount	$	442,535		$	469,119
Accumulated amortization	(242,422		)	(219,654		)
Net	$	200,113		$	249,465

Amortization of acquired below-market lease value, net of acquired above-market lease value, resulted in a change in rental revenues of $(27.3) million, $(2.2) million and $8.3 million for the years ended December 31, 2018, 2017 and 2016, respectively. The expected average remaining lives for acquired below-market leases and acquired above-market leases is 8.1 years and 2.8 years, respectively, as of December 31, 2018. Estimated annual amortization of acquired below-market lease value, net of acquired above-market lease value, for each of the five succeeding years and thereafter, commencing January 1, 2019 is as follows:



(Amounts in thousands)
2019	$	(15,323	)
2020	(3,915		)
2021	872
2022	7,898
2023	12,045
Thereafter	78,777
Total	$	80,354

Amortization of acquired in-place lease value (a component of depreciation and amortization expense) was $211.0 million, $101.2 million and $52.6 million for the years ended December 31, 2018, 2017 and 2016, respectively. The expected average amortization period for acquired in-place lease value is 6.4 years as of December 31, 2018. The weighted average remaining contractual life for acquired leases excluding renewals or extensions is 5.9 years as of December 31, 2018. Estimated annual amortization of acquired in-place lease value for each of the five succeeding years and thereafter, commencing January 1, 2019 is as follows:



(Amounts in thousands)
2019	$	158,095
2020	123,450
2021	98,916
2022	77,056
2023	65,518
Thereafter	251,333
Total	$	774,368

Amortization of tenant relationship value and trade names (a component of depreciation and amortization expense) was approximately $123.5 million and $0, respectively, for the year ended December 31, 2018, $85.9 million and $0, respectively, for the year ended December 31, 2017 and $67.2 million and $6.9 million, respectively for the year ended December 31, 2016. During the year ended December 31, 2016, management of the Company decided to retire the Telx trade name. Accordingly, the Company wrote off the net remaining balance of approximately $6.1 million. The weighted average remaining contractual life for tenant relationship value is 14.8 years. Estimated annual amortization of tenant relationship value for each of the five succeeding years and thereafter, commencing January 1, 2019 is as follows:



(Amounts in thousands)
2019	$	143,818
2020	143,818
2021	143,818
2022	143,818
2023	143,818
Thereafter	1,328,698
Total	$	2,047,788