Revenue Recognition (Schedule of Revenues by Segment) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Lease revenues	$ 388,205	$ 369,879	$ 1,160,061	$ 1,127,005
Total revenues	467,657	453,700	1,389,004	1,356,716
Rental revenues
Disaggregation of Revenue [Line Items]
Revenue	409,621	389,097	1,213,878	1,176,104
Total revenues	409,621	389,097	1,213,878	1,176,104
Lease revenues
Disaggregation of Revenue [Line Items]
Lease revenues	388,205	369,879	1,160,061	1,127,005
Property rentals
Disaggregation of Revenue [Line Items]
Lease revenues	377,816	360,416	1,131,426	1,103,097
Trade shows
Disaggregation of Revenue [Line Items]
Lease revenues	7,847	6,956	21,026	19,807
Sales-type lease income
Disaggregation of Revenue [Line Items]
Lease revenues	2,542	2,507	7,609	4,101
Tenant services
Disaggregation of Revenue [Line Items]
Revenue	16,099	14,158	38,128	34,177
Parking revenues
Disaggregation of Revenue [Line Items]
Revenue	5,317	5,060	15,689	14,922
Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	58,036	64,603	175,126	180,612
Total revenues	58,036	64,603	175,126	180,612
BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	35,372	42,530	108,059	116,437
Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	2,820	2,998	8,193	8,954
Other income
Disaggregation of Revenue [Line Items]
Revenue	19,844	19,075	58,874	55,221
New York
Disaggregation of Revenue [Line Items]
Total revenues	380,212	365,654	1,138,014	1,096,722
New York \| Rental revenues
Disaggregation of Revenue [Line Items]
Revenue	325,999	305,112	974,373	929,562
New York \| Lease revenues
Disaggregation of Revenue [Line Items]
Lease revenues	310,935	291,887	935,425	893,915
New York \| Property rentals
Disaggregation of Revenue [Line Items]
Lease revenues	308,393	289,380	927,816	889,814
New York \| Trade shows
Disaggregation of Revenue [Line Items]
Lease revenues	0	0	0	0
New York \| Sales-type lease income
Disaggregation of Revenue [Line Items]
Lease revenues	2,542	2,507	7,609	4,101
New York \| Tenant services
Disaggregation of Revenue [Line Items]
Revenue	10,948	9,333	26,785	23,990
New York \| Parking revenues
Disaggregation of Revenue [Line Items]
Revenue	4,116	3,892	12,163	11,657
New York \| Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	54,213	60,542	163,641	167,160
New York \| BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	38,101	44,902	116,018	123,143
New York \| Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	3,072	3,170	8,695	9,525
New York \| Other income
Disaggregation of Revenue [Line Items]
Revenue	13,040	12,470	38,928	34,492
Other
Disaggregation of Revenue [Line Items]
Total revenues	87,445	88,046	250,990	259,994
Other \| Rental revenues
Disaggregation of Revenue [Line Items]
Revenue	83,622	83,985	239,505	246,542
Other \| Lease revenues
Disaggregation of Revenue [Line Items]
Lease revenues	77,270	77,992	224,636	233,090
Other \| Property rentals
Disaggregation of Revenue [Line Items]
Lease revenues	69,423	71,036	203,610	213,283
Other \| Trade shows
Disaggregation of Revenue [Line Items]
Lease revenues	7,847	6,956	21,026	19,807
Other \| Sales-type lease income
Disaggregation of Revenue [Line Items]
Lease revenues	0	0	0	0
Other \| Tenant services
Disaggregation of Revenue [Line Items]
Revenue	5,151	4,825	11,343	10,187
Other \| Parking revenues
Disaggregation of Revenue [Line Items]
Revenue	1,201	1,168	3,526	3,265
Other \| Fee and other income
Disaggregation of Revenue [Line Items]
Revenue	3,823	4,061	11,485	13,452
Other \| BMS cleaning fees
Disaggregation of Revenue [Line Items]
Revenue	(2,729)	(2,372)	(7,959)	(6,706)
Other \| Management and leasing fees
Disaggregation of Revenue [Line Items]
Revenue	(252)	(172)	(502)	(571)
Other \| Other income
Disaggregation of Revenue [Line Items]
Revenue	$ 6,804	$ 6,605	$ 19,946	$ 20,729