Acquired Intangible Assets and Liabilities

The following summarizes our acquired intangible assets (real estate intangibles, comprised of acquired in-place lease value, tenant relationship value and trade name along with acquired above-market lease value) and intangible liabilities (acquired below-market lease value) as of December 31, 2016 and 2015.



	Balance as of
(Amounts in thousands)	December 31, 2016			December 31, 2015
Real Estate Intangibles:
Acquired in-place lease value:
Gross amount	$	896,693		$	901,381
Accumulated amortization	(517,443		)	(472,933		)
Net	$	379,250		$	428,448
Tenant relationship value:
Gross amount	$	971,519		$	734,800
Accumulated amortization	(82,069		)	(14,495		)
Net	$	889,450		$	720,305
Trade name:
Gross amount	$	7,300		$	7,300
Accumulated amortization	(7,300		)	(417		)
Net	$	—		$	6,883
Acquired above-market leases:
Gross amount	$	110,142		$	122,311
Accumulated amortization	(87,961		)	(89,613		)
Net	$	22,181		$	32,698
Acquired below-market leases:
Gross amount	$	283,899		$	294,791
Accumulated amortization	(202,000		)	(193,677		)
Net	$	81,899		$	101,114

Amortization of acquired below-market lease value, net of acquired above-market lease value, resulted in an increase to rental revenues of $7.5 million, $9.3 million and $10.0 million for the years ended December 31, 2016 , 2015 and 2014, respectively. The expected average remaining lives for acquired below-market leases and acquired above-market leases is 6.5 years and 4.1 years, respectively, as of December 31, 2016. 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, 2017 is as follows:



(Amounts in thousands)
2017	$	7,216
2018	5,566
2019	5,698
2020	7,422
2021	7,114
Thereafter	26,702
Total	$	59,718

Amortization of acquired in place lease value (a component of depreciation and amortization expense) was $52.6 million, $46.2 million and $62.2 million for the years ended December 31, 2016, 2015 and 2014, respectively. The expected average amortization period for acquired in place lease value is 8.0 years as of December 31, 2016. The weighted average remaining contractual life for acquired leases excluding renewals or extensions is 7.0 years as of December 31, 2016. Estimated annual amortization of acquired in-place lease value for each of the five succeeding years and thereafter, commencing January 1, 2017 is as follows:



(Amounts in thousands)
2017	$	54,088
2018	47,640
2019	40,515
2020	36,561
2021	33,958
Thereafter	166,488
Total	$	379,250

Amortization of tenant relationship value and trade names (a component of depreciation and amortization expense) was approximately $67.2 million and $6.9 million, respectively for the year ended December 31, 2016, $14.5 million and $0.4 million, respectively for the year ended December 31, 2015 and $0 in 2014. 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 customer contracts is 13.0 years. Estimated annual amortization of customer contracts for each of the five succeeding years and thereafter, commencing January 1, 2017 is as follows:



(Amounts in thousands)
2017	$	69,608
2018	69,608
2019	69,608
2020	69,608
2021	69,608
Thereafter	541,410
Total	$	889,450