Identified Intangible Assets and Liabilities

12 Months Ended

Dec. 31, 2014

Identified Intangible Assets and Liabilities [Abstract]

Identified Intangible Assets and Intangible Liabilities

9. Identified Intangible Assets and Liabilities

The following summarizes our identified intangible assets (primarily acquired above-market leases) and liabilities (primarily acquired below-market leases) as of December 31, 2014 and2013.

	Balance as of December 31,
(Amounts in thousands)	2014		2013
Identified intangible assets:
Gross amount	$	502,080	$	583,862
Accumulated amortization		(225,841)		(276,426)
Net	$	276,239	$	307,436
Identified intangible liabilities (included in deferred revenue):
Gross amount	$	885,763	$	855,860
Accumulated amortization		(396,895)		(359,371)
Net	$	488,868	$	496,489

Amortization of acquired below-market leases, net of acquired above-market leases resulted in an increase to rental income of $46,277,000, $50,128,000 and $51,271,000 for the years ended December 31, 2014, 2013 and 2012, respectively. Estimated annual amortization of acquired below-market leases, net of acquired above-market leases for each of the five succeeding years commencing January 1, 2015 is as follows:

(Amounts in thousands)
2015	$	57,202
2016		45,333
2017		42,457
2018		41,311
2019		30,950

Amortization of all other identified intangible assets (a component of depreciation and amortization expense) was $29,870,000, $64,196,000 and $49,442,000for the years ended December 31, 2014, 2013 and 2012, respectively. Estimated annual amortization of all other identified intangible assets including acquired in-place leases, customer relationships, and third party contracts for each of the five succeeding years commencing January 1, 2015 is as follows:

(Amounts in thousands)
2015	$	27,210
2016		21,437
2017		17,859
2018		13,533
2019		11,553

We are a tenant under ground leases at certain properties. Amortization of these acquired below-market leases, net of above-market leases resulted in an increase to rent expense of $3,363,000, $4,290,000 and $1,261,000 for the years ended December 31, 2014, 2013 and 2012, respectively. Estimated annual amortization of these below-market leases, net of above-market leases for each of the five succeeding years commencing January 1, 2015 is as follows:

(Amounts in thousands)
2015	$	3,363
2016		3,363
2017		3,363
2018		3,363
2019		3,363