Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Accounting Policies [Abstract]

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 March 31, 2021 and December 31, 2020 (in thousands):

	March 31, 2021		December 31, 2020
Identified intangible assets (included in other assets):
Gross amount	$	239,562	$	215,673
Accumulated amortization	(204,386)		(190,523)
Net(1)	$	35,176	$	25,150
Identified intangible liabilities (included in deferred revenue):
Gross amount	$	242,334	$	241,409
Accumulated amortization	(233,766)		(230,479)
Net(1)	$	8,568	$	10,930

(1) As of March 31, 2021 and December 31, 2020, no net intangible assets and no net intangible liabilities were reclassified to assets held for sale or liabilities related to assets held for sale.

Schedule of marketable securities

At March 31, 2021 and December 31, 2020, we held the following marketable securities (in thousands):

	March 31, 2021		December 31, 2020
Commercial mortgage-backed securities	$	23,784	$	28,570
Total marketable securities available-for-sale	$	23,784	$	28,570

Schedules of Concentration of Risk, by Risk Factor

For the three months ended March 31, 2021, the following properties contributed more than 5.0% of our annualized cash rent from office properties, including our share of annualized cash rent from joint venture office properties:

Property	Three months ended March 31, 2021
11 Madison Avenue	9.2%
420 Lexington Avenue (Graybar)	7.2%
1185 Avenue of the Americas	7.1%
1515 Broadway	6.9%
220 East 42nd Street	6.2%
280 Park Avenue	5.8%
485 Lexington Avenue	5.1%