Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 60,075	$ 32,844	$ 80,509
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization, including amortization of debt issuance costs	36,515	38,499	38,681
Straight-lining of rental income	2,413	5,924	4,297
Stock-based compensation expense	394	394	394
Change in fair value of marketable securities	8,757	11,990	0
Change in operating assets and liabilities:
Tenant and other receivables, net	(2,017)	(1,382)	363
Other assets	21,553	(1,197)	(2,627)
Amounts due to Vornado	789	(1,907)	1,626
Accounts payable and accrued expenses	(1,800)	(11,760)	211
Other liabilities	(609)	133	(28)
Net cash provided by operating activities	126,070	73,538	123,426
CASH FLOWS FROM INVESTING ACTIVITIES
Construction in progress and real estate additions	(9,449)	(3,966)	(3,434)
Rego Park II loan participation	0	0	(200,000)
Repayment of Rego Park II loan participation	0	2,829	1,463
Net cash used in investing activities	(9,449)	(1,137)	(201,971)
CASH FLOWS FROM FINANCING ACTIVITIES
Dividends paid	(92,124)	(92,100)	(86,961)
Debt issuance costs	(15)	(2,189)	(12,186)
Debt repayments	0	(160,142)	(303,707)
Proceeds from borrowing	0	78,246	500,000
Net cash (used in) provided by financing activities	(92,139)	(176,185)	97,146
Net increase (decrease) in cash and cash equivalents and restricted cash	24,482	(103,784)	18,601
Cash and cash equivalents and restricted cash at beginning of year	289,495	393,279	374,678
Cash and cash equivalents and restricted cash at end of year	313,977	289,495	393,279
RECONCILIATION OF CASH AND CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents at beginning of year	283,056	307,536	288,926
Restricted cash at beginning of year	6,439	85,743	85,752
Cash and cash equivalents and restricted cash at beginning of year	289,495	393,279	374,678
Cash and cash equivalents at end of year	298,063	283,056	307,536
Restricted cash at end of year	15,914	6,439	85,743
Cash and cash equivalents and restricted cash at end of year	313,977	289,495	393,279
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash payments for interest	34,669	38,231	26,994
NON-CASH TRANSACTIONS
Lease liability arising from the recognition of right-of-use asset	5,428	0	0
Liability for real estate additions, including $18, $125 and $21 for development fees due to Vornado in 2019, 2018 and 2017, respectively	3,191	631	705
Reclassification of prepaid real estate taxes to construction in progress for property in redevelopment	1,466	0	0
Write-off of fully amortized and/or depreciated assets	0	16,090	4,265
Derecognition of Rego Park II loan participation asset (see Note 2)	$ 0	$ 195,708	$ 0