Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Properties are depreciated using the straight-line method over the estimated useful lives of the assets. The estimated useful lives are as follows:



Category		Term
Building (fee ownership)		40 years
Building improvements		shorter of remaining life of the building or useful life
Building (leasehold interest)		lesser of 40 years or remaining term of the lease
Property under capital lease		remaining lease term
Furniture and fixtures		four to seven years
Tenant improvements		shorter of remaining term of the lease or useful life

Schedule of marketable securities

At December 31, 2018 and 2017, we held the following marketable securities (in thousands):



	December 31,
	2018		2017
Commercial mortgage-backed securities	$	28,638	$	28,579
Total marketable securities available-for-sale	$	28,638	$	28,579

Summary of identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases)

The following summarizes our identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases) as of December 31, 2018 and 2017 (in thousands):



	December 31,
	2018			2017
Identified intangible assets (included in other assets):
Gross amount	$	266,540		$	325,880
Accumulated amortization	(241,040		)	(277,038		)
Net⁽¹⁾	$	25,500		$	48,842
Identified intangible liabilities (included in deferred revenue):
Gross amount	$	276,245		$	540,283
Accumulated amortization	(253,767		)	(402,583		)
Net⁽¹⁾	$	22,478		$	137,700


(1)	As of December 31, 2018, no net intangible assets and no net intangible liabilities were reclassified to assets held for sale and liabilities related to assets held for sale. As of December 31, 2017, $13.9 million net intangible assets and $4.1 million net intangible liabilities were reclassified to assets held for sale and liabilities related to assets held for sale.

Schedule of estimated annual amortization of acquired above-market leases, net of acquired below-market leases

The estimated annual amortization of acquired above-market leases, net of acquired (below-market) leases (a component of rental revenue), for each of the five succeeding years is as follows (in thousands):



2019	$	(5,227	)
2020	(3,655		)
2021	(1,631		)
2022	(1,328		)
2023	(749		)

Schedule of estimated annual amortization of all other identifiable assets

The estimated annual amortization of all other identifiable assets (a component of depreciation and amortization expense) including tenant improvements for each of the five succeeding years is as follows (in thousands):



2019	$	9,825
2020	4,817
2021	3,454
2022	1,892
2023	1,507

Schedules of concentration of risk, by risk factor

For the years ended December 31, 2018, 2017, and 2016, the following properties contributed more than 5.0% of our annualized cash rent, including our share of joint venture annualized cash rent:



Property	2018	Property	2017	Property	2016
11 Madison Avenue	7.4%	11 Madison Avenue	7.1%	1515 Broadway	8.8%
1185 Avenue of the Americas	6.7%	1185 Avenue of the Americas	7.1%	1185 Avenue of the Americas	6.9%
420 Lexington Avenue	6.5%	1515 Broadway	7.0%	11 Madison Avenue	6.1%
1515 Broadway	6.0%	420 Lexington Avenue	6.0%	420 Lexington Avenue	5.9%
One Madison Avenue	5.8%	One Madison Avenue	5.6%	One Madison Avenue	5.6%