Real Estate Intangibles

3 Months Ended

Mar. 31, 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):


		March 31, 2016		December 31, 2015
Assets:
	In place lease intangibles	$	1,196,335	$	1,179,537
	Above market tenant leases		62,544		67,529
	Below market ground leases		62,643		80,224
	Lease commissions		24,542		23,295
	Gross historical cost		1,346,064		1,350,585
	Accumulated amortization		(923,712)		(881,096)
	Net book value	$	422,352	$	469,489

	Weighted-average amortization period in years		14.6		13.4

Liabilities:
	Below market tenant leases	$	93,054	$	93,089
	Above market ground leases		7,908		7,907
	Gross historical cost		100,962		100,996
	Accumulated amortization		(47,983)		(46,048)
	Net book value	$	52,979	$	54,948

	Weighted-average amortization period in years		14.7		14.5

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


	Three Months Ended
	March 31,
	2016		2015
Rental income related to above/below market tenant leases, net	$	81	$	206
Property operating expenses related to above/below market ground leases, net		(311)		(319)
Depreciation and amortization related to in place lease intangibles and lease commissions		(34,454)		(24,324)

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


		Assets		Liabilities
2016	$	84,239	$	3,894
2017		79,195		6,807
2018		44,698		6,181
2019		25,238		5,771
2020		22,341		5,290
Thereafter		166,641		25,036
Total	$	422,352	$	52,979