Real Estate Intangibles

9 Months Ended

Sep. 30, 2015

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, 2015		December 31, 2014
Assets:
	In place lease intangibles	$	1,042,770	$	988,290
	Above market tenant leases		82,083		65,684
	Below market ground leases		61,159		62,426
	Lease commissions		22,498		19,536
	Gross historical cost		1,208,510		1,135,936
	Accumulated amortization		(836,684)		(776,501)
	Net book value	$	371,826	$	359,435

	Weighted-average amortization period in years		17.2		17.7

Liabilities:
	Below market tenant leases	$	89,891	$	91,168
	Above market ground leases		7,860		7,859
	Gross historical cost		97,751		99,027
	Accumulated amortization		(44,609)		(40,891)
	Net book value	$	53,142	$	58,136

	Weighted-average amortization period in years		15.6		14.4

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,
	2015		2014		2015		2014
Rental income related to above/below market tenant leases, net	$	(1,684)	$	179	$	(1,901)	$	423
Property operating expenses related to above/below market ground leases, net		(308)		(317)		(962)		(926)
Depreciation and amortization related to in place lease intangibles and lease commissions		(26,137)		(46,366)		(82,434)		(185,363)

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


		Assets		Liabilities
2015	$	39,972	$	3,279
2016		71,453		6,512
2017		43,426		6,052
2018		30,094		5,583
2019		24,033		5,325
Thereafter		162,848		26,391
Total	$	371,826	$	53,142