Real Estate Intangibles

3 Months Ended

Mar. 31, 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):


		March 31, 2015		December 31, 2014
Assets:
	In place lease intangibles	$	1,037,697	$	988,290
	Above market tenant leases		66,162		65,684
	Below market ground leases		62,426		62,426
	Lease commissions		20,809		19,536
	Gross historical cost		1,187,094		1,135,936
	Accumulated amortization		(789,546)		(776,501)
	Net book value	$	397,548	$	359,435

	Weighted-average amortization period in years		16.2		17.7

Liabilities:
	Below market tenant leases	$	91,365	$	91,168
	Above market ground leases		7,859		7,859
	Gross historical cost		99,224		99,027
	Accumulated amortization		(42,853)		(40,891)
	Net book value	$	56,371	$	58,136

	Weighted-average amortization period in years		14.4		14.4

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


	Three Months Ended
	March 31,
	2015		2014
Rental income related to above/below market tenant leases, net	$	206	$	(45)
Property operating expenses related to above/below market ground leases, net		(319)		(311)
Depreciation and amortization related to in place lease intangibles and lease commissions		(24,324)		(79,393)

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


		Assets		Liabilities
2015	$	72,406	$	$3,323
2016		60,019		8,176
2017		37,369		8,594
2018		26,596		8,500
2019		23,289		6,819
Thereafter		177,869		20,959
Total	$	397,548	$	56,371