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Segment Information (Schedule Of Segment Reporting By Geographic Area And Property Type) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 3,328,778 | $ 3,262,439 | $ 3,119,999
Rental Revenue: Residential | 50,543 | 49,508 | 47,592
Rental Revenue Total | $ 3,429,317 | $ 3,363,171 | $ 3,214,948
Rental Revenue: % of Grand Totals | 100.00% | 100.00% | 100.00%
Rental Expenses: Office | $ 1,308,881 | $ 1,263,366 | $ 1,160,697
Rental Expenses: Residential | 26,188 | 23,472 | 23,250
Rental Expenses: Total | $ 1,370,668 | $ 1,322,126 | $ 1,216,172
Rental Expenses: % Of Grand Totals | 100.00% | 100.00% | 100.00%
Net Operating Income | $ 2,058,649 | $ 2,041,045 | $ 1,998,776
Net Operating Income: % of Grand Totals | 100.00% | 100.00% | 100.00%
Company's Share of Net Operating Income: % of Grand Totals | 100.00% | 100.00% | 100.00%
Boston [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 1,218,009 | $ 1,159,460 | $ 1,093,840
Rental Revenue: Residential | 17,909 | 17,198 | 16,452
Rental Revenue Total | $ 1,285,914 | $ 1,227,882 | $ 1,157,649
Rental Revenue: % of Grand Totals | 37.49% | 36.51% | 36.01%
Rental Expenses: Office | $ 455,880 | $ 427,446 | $ 393,339
Rental Expenses: Residential | 8,910 | 6,495 | 6,378
Rental Expenses: Total | $ 500,389 | $ 469,229 | $ 431,942
Rental Expenses: % Of Grand Totals | 36.52% | 35.49% | 35.51%
Net Operating Income | $ 785,525 | $ 758,653 | $ 725,707
Net Operating Income: % of Grand Totals | 38.16% | 37.18% | 36.31%
Company's Share of Net Operating Income: % of Grand Totals | 38.29% | 37.67% | 36.35%
Los Angeles [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 70,519 | $ 75,353 | $ 3,890
Rental Revenue: Residential | 0 | 0 | 0
Rental Revenue Total | $ 70,519 | $ 75,353 | $ 3,890
Rental Revenue: % of Grand Totals | 2.06% | 2.24% | 0.12%
Rental Expenses: Office | $ 22,108 | $ 27,537 | $ 1,431
Rental Expenses: Residential | 0 | 0 | 0
Rental Expenses: Total | $ 22,108 | $ 27,537 | $ 1,431
Rental Expenses: % Of Grand Totals | 1.61% | 2.08% | 0.12%
Net Operating Income | $ 48,411 | $ 47,816 | $ 2,459
Net Operating Income: % of Grand Totals | 2.35% | 2.35% | 0.12%
Company's Share of Net Operating Income: % of Grand Totals | 3.88% | 3.79% | 2.61%
New York [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 1,054,594 | $ 1,042,460 | $ 1,053,615
Rental Revenue: Residential | 0 | 0 | 0
Rental Revenue Total | $ 1,054,594 | $ 1,042,460 | $ 1,053,615
Rental Revenue: % of Grand Totals | 30.75% | 31.00% | 32.77%
Rental Expenses: Office | $ 453,192 | $ 437,600 | $ 415,831
Rental Expenses: Residential | 0 | 0 | 0
Rental Expenses: Total | $ 453,192 | $ 437,600 | $ 415,831
Rental Expenses: % Of Grand Totals | 33.06% | 33.10% | 34.19%
Net Operating Income | $ 601,402 | $ 604,860 | $ 637,784
Net Operating Income: % of Grand Totals | 29.21% | 29.63% | 31.91%
Company's Share of Net Operating Income: % of Grand Totals | 23.67% | 24.21% | 25.62%
San Francisco [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 509,920 | $ 522,463 | $ 539,904
Rental Revenue: Residential | 14,017 | 13,668 | 14,102
Rental Revenue Total | $ 523,937 | $ 536,131 | $ 554,006
Rental Revenue: % of Grand Totals | 15.28% | 15.94% | 17.23%
Rental Expenses: Office | $ 203,565 | $ 199,324 | $ 194,205
Rental Expenses: Residential | 9,060 | 8,940 | 9,255
Rental Expenses: Total | $ 212,625 | $ 208,264 | $ 203,460
Rental Expenses: % Of Grand Totals | 15.51% | 15.75% | 16.73%
Net Operating Income | $ 311,312 | $ 327,867 | $ 350,546
Net Operating Income: % of Grand Totals | 15.12% | 16.06% | 17.54%
Company's Share of Net Operating Income: % of Grand Totals | 16.58% | 17.45% | 18.66%
Seattle |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 49,269 | $ 44,080 | $ 63,830
Rental Revenue: Residential | 0 | 0 | 0
Rental Revenue Total | $ 49,269 | $ 44,080 | $ 63,830
Rental Revenue: % of Grand Totals | 1.44% | 1.31% | 1.99%
Rental Expenses: Office | $ 12,491 | $ 13,170 | $ 12,387
Rental Expenses: Residential | 0 | 0 | 0
Rental Expenses: Total | $ 12,491 | $ 13,170 | $ 12,387
Rental Expenses: % Of Grand Totals | 0.91% | 1.00% | 1.02%
Net Operating Income | $ 36,778 | $ 30,910 | $ 51,443
Net Operating Income: % of Grand Totals | 1.79% | 1.51% | 2.57%
Company's Share of Net Operating Income: % of Grand Totals | 2.32% | 1.95% | 3.00%
Washington, DC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Rental Revenue: Office | $ 426,467 | $ 418,623 | $ 364,920
Rental Revenue: Residential | 18,617 | 18,642 | 17,038
Rental Revenue Total | $ 445,084 | $ 437,265 | $ 381,958
Rental Revenue: % of Grand Totals | 12.98% | 13.00% | 11.88%
Rental Expenses: Office | $ 161,645 | $ 158,289 | $ 143,504
Rental Expenses: Residential | 8,218 | 8,037 | 7,617
Rental Expenses: Total | $ 169,863 | $ 166,326 | $ 151,121
Rental Expenses: % Of Grand Totals | 12.39% | 12.58% | 12.43%
Net Operating Income | $ 275,221 | $ 270,939 | $ 230,837
Net Operating Income: % of Grand Totals | 13.37% | 13.27% | 11.55%
Company's Share of Net Operating Income: % of Grand Totals | 15.26% | 14.93% | 13.76%
Hotel [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | $ 49,996 | $ 51,224 | $ 47,357
Operating expense | 35,599 | 35,288 | 32,225
Hotel [Member] | Boston [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 49,996 | 51,224 | 47,357
Operating expense | 35,599 | 35,288 | 32,225
Hotel [Member] | Los Angeles [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 0 | 0 | 0
Operating expense | 0 | 0 | 0
Hotel [Member] | New York [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 0 | 0 | 0
Operating expense | 0 | 0 | 0
Hotel [Member] | San Francisco [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 0 | 0 | 0
Operating expense | 0 | 0 | 0
Hotel [Member] | Seattle |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 0 | 0 | 0
Operating expense | 0 | 0 | 0
Hotel [Member] | Washington, DC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Other revenue | 0 | 0 | 0
Operating expense | 0 | 0 | 0
Noncontrolling interest - property partnerships [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | (204,433) | (186,707) | (194,365)
Noncontrolling interest - property partnerships [Member] | Boston [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | (64,069) | (46,487) | (45,730)
Noncontrolling interest - property partnerships [Member] | Los Angeles [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 0 | 0 | 0
Noncontrolling interest - property partnerships [Member] | New York [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | (140,364) | (140,220) | (148,635)
Noncontrolling interest - property partnerships [Member] | San Francisco [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 0 | 0 | 0
Noncontrolling interest - property partnerships [Member] | Seattle |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 0 | 0 | 0
Noncontrolling interest - property partnerships [Member] | Washington, DC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 0 | 0 | 0
Unconsolidated Joint Ventures [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 122,569 | 129,718 | 160,695
Unconsolidated Joint Ventures [Member] | Boston [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 35,274 | 35,298 | 34,376
Unconsolidated Joint Ventures [Member] | Los Angeles [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 28,381 | 27,367 | 48,818
Unconsolidated Joint Ventures [Member] | New York [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 6,853 | 15,612 | 14,314
Unconsolidated Joint Ventures [Member] | San Francisco [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 16,537 | 18,312 | 16,203
Unconsolidated Joint Ventures [Member] | Seattle |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 9,023 | 7,788 | 7,494
Unconsolidated Joint Ventures [Member] | Washington, DC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 26,501 | 25,341 | 39,490
Company's Share [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 1,976,785 | 1,984,056 | 1,965,106
Company's Share [Member] | Boston [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 756,730 | 747,464 | 714,353
Company's Share [Member] | Los Angeles [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 76,792 | 75,183 | 51,277
Company's Share [Member] | New York [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 467,891 | 480,252 | 503,463
Company's Share [Member] | San Francisco [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 327,849 | 346,179 | 366,749
Company's Share [Member] | Seattle |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | 45,801 | 38,698 | 58,937
Company's Share [Member] | Washington, DC [Member] |  |  |
Segment Reporting Information [Line Items] |  |  |
Net Operating Income | $ 301,722 | $ 296,280 | $ 270,327

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