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, 2017 and 2016.



	Balance as of
(Amounts in thousands)	December 31, 2017			December 31, 2016
Real Estate Intangibles:
Acquired in-place lease value:
Gross amount	$	1,473,515		$	896,693
Accumulated amortization	(613,948		)	(517,443		)
Net	$	859,567		$	379,250
Tenant relationship value:
Gross amount	$	1,978,277		$	971,519
Accumulated amortization	(169,919		)	(82,069		)
Net	$	1,808,358		$	889,450
Trade name:
Gross amount	$	—		$	7,300
Accumulated amortization	—			(7,300		)
Net	$	—		$	—
Acquired above-market leases:
Gross amount	$	294,514		$	110,142
Accumulated amortization	(110,139		)	(87,961		)
Net	$	184,375		$	22,181
Acquired below-market leases:
Gross amount	$	469,119		$	283,899
Accumulated amortization	(219,654		)	(202,000		)
Net	$	249,465		$	81,899

Amortization of acquired below-market lease value, net of acquired above-market lease value, resulted in a change in rental revenues of $(2.2) million, $8.3 million and $9.3 million for the years ended December 31, 2017, 2016 and 2015, respectively. The expected average remaining lives for acquired below-market leases and acquired above-market leases is 9.2 years and 3.9 years, respectively, as of December 31, 2017. 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, 2018 is as follows:



(Amounts in thousands)
2018	$	(26,622	)
2019	(15,372		)
2020	(3,151		)
2021	2,055
2022	9,054
Thereafter	99,126
Total	$	65,090

Amortization of acquired in-place lease value (a component of depreciation and amortization expense) was $101.2 million, $52.6 million and $46.2 million for the years ended December 31, 2017, 2016 and 2015, respectively. The expected average amortization period for acquired in-place lease value is 6.6 years as of December 31, 2017. The weighted average remaining contractual life for acquired leases excluding renewals or extensions is 6.1 years as of December 31, 2017. Estimated annual amortization of acquired in-place lease value for each of the five succeeding years and thereafter, commencing January 1, 2018 is as follows:



(Amounts in thousands)
2018	$	209,091
2019	147,137
2020	111,205
2021	86,583
2022	64,666
Thereafter	240,885
Total	$	859,567

Amortization of tenant relationship value and trade names (a component of depreciation and amortization expense) was approximately $85.9 million and $0, respectively, for the year ended December 31, 2017, $67.2 million and $6.9 million, respectively, for the year ended December 31, 2016 and $14.5 million and $0.4 million, respectively for the year ended December 31, 2015. During the quarter ended June 30, 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 15.3 years. Estimated annual amortization of tenant relationship value for each of the five succeeding years and thereafter, commencing January 1, 2018 is as follows:



(Amounts in thousands)
2018	$	123,786
2019	123,786
2020	123,786
2021	123,786
2022	123,792
Thereafter	1,189,422
Total	$	1,808,358