Real Estate Intangibles

9 Months Ended

Sep. 30, 2016

4. Real Estate Intangibles

The following is a summary of our real estate intangibles, excluding those classified as held for sale, as of the dates indicated (dollars in thousands):


		September 30, 2016		December 31, 2015
Assets:
	In place lease intangibles	$	1,272,177	$	1,179,537
	Above market tenant leases		62,544		67,529
	Below market ground leases		62,257		80,224
	Lease commissions		26,054		23,295
	Gross historical cost		1,423,032		1,350,585
	Accumulated amortization		(971,883)		(881,096)
	Net book value	$	451,149	$	469,489

	Weighted-average amortization period in years		14.0		13.4

Liabilities:
	Below market tenant leases	$	93,507	$	93,089
	Above market ground leases		8,107		7,907
	Gross historical cost		101,614		100,996
	Accumulated amortization		(51,727)		(46,048)
	Net book value	$	49,887	$	54,948

	Weighted-average amortization period in years		15.4		14.5

The following is a summary of real estate intangible amortization for the periods presented (in thousands):


	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2016		2015		2016		2015
Rental income related to above/below market tenant leases, net	$	278	$	(1,684)	$	569	$	(1,901)
Property operating expenses related to above/below market ground leases, net		(309)		(308)		(931)		(962)
Depreciation and amortization related to in place lease intangibles and lease commissions		(30,137)		(26,137)		(95,610)		(82,434)

The future estimated aggregate amortization of intangible assets and liabilities is as follows for the periods presented (in thousands):


		Assets		Liabilities
2016	$	45,156	$	1,810
2017		122,892		6,819
2018		70,566		6,234
2019		29,877		5,825
2020		22,830		5,344
Thereafter		159,828		23,855
Total	$	451,149	$	49,887