Segment Reporting (Schedule Of Selected Results Of Operations And Asset Information) (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Segment Reporting Information [Line Items]          
Total revenues $ 132,114 $ 160,018 $ 397,670 $ 472,671  
Total operating and interest expenses 89,040 103,311 270,124 302,494  
Equity in earnings (loss) of unconsolidated joint ventures (687) (1,533) 833 (4,882)  
Net operating income (loss) 42,387 55,174 128,379 165,295  
Total assets 5,046,194   5,046,194   $ 4,957,885
Total long-lived assets 4,439,429   4,439,429   4,291,126
Total investments in unconsolidated joint ventures 230,614   230,614   252,626
Commercial And Other Real Estate [Member]          
Segment Reporting Information [Line Items]          
Total revenues 100,489 133,962 317,467 403,830  
Total operating and interest expenses 43,774 60,524 140,872 182,447  
Equity in earnings (loss) of unconsolidated joint ventures 713 1,058 1,482 1,453  
Net operating income (loss) 57,428 74,496 178,077 222,836  
Total assets 2,734,813   2,734,813   2,915,646
Total long-lived assets 2,439,588   2,439,588   2,613,815
Total investments in unconsolidated joint ventures 13,464   13,464   15,143
Multiple-Family Real Estate & Services [Member]          
Segment Reporting Information [Line Items]          
Total revenues 30,942 24,606 79,582 65,813  
Total operating and interest expenses 19,272 16,725 51,563 47,722  
Equity in earnings (loss) of unconsolidated joint ventures (1,400) (2,591) (649) (6,335)  
Net operating income (loss) 10,270 5,290 27,370 11,756  
Total assets 2,246,208   2,246,208   1,937,708
Total long-lived assets 1,966,570   1,966,570   1,645,410
Total investments in unconsolidated joint ventures 216,902   216,902   237,321
Corporate & Other [Member]          
Segment Reporting Information [Line Items]          
Total revenues 683 1,450 621 3,028  
Total operating and interest expenses 25,994 26,062 77,689 72,325  
Net operating income (loss) (25,311) $ (24,612) (77,068) $ (69,297)  
Total assets 65,173   65,173   104,531
Total long-lived assets 33,271   33,271   31,901
Total investments in unconsolidated joint ventures $ 248   $ 248   $ 162