Segment Reporting (Schedule Of Selected Results Of Operations And Asset Information) (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Segment Reporting Information [Line Items]          
Total revenues $ 126,589 $ 162,766 $ 265,556 $ 312,653  
Total operating and interest expenses 84,633 101,877 181,084 199,183  
Equity in earnings (loss) of unconsolidated joint ventures (52) (3,298) 1,520 (3,349)  
Net operating income (loss) 41,904 57,591 85,992 110,121  
Total assets 4,858,284   4,858,284   $ 4,957,885
Total long-lived assets 4,245,330   4,245,330   4,291,126
Total investments in unconsolidated joint ventures 247,607   247,607   252,626
Commercial And Other Real Estate [Member]          
Segment Reporting Information [Line Items]          
Total revenues 101,792 138,003 216,978 269,869  
Total operating and interest expenses 43,116 55,620 97,097 113,670  
Equity in earnings (loss) of unconsolidated joint ventures 909 (18) 769 394  
Net operating income (loss) 59,585 82,365 120,650 156,593  
Total assets 2,751,750   2,751,750   2,915,646
Total long-lived assets 2,478,007   2,478,007   2,613,815
Total investments in unconsolidated joint ventures 15,110   15,110   15,143
Multiple-Family Real Estate & Services [Member]          
Segment Reporting Information [Line Items]          
Total revenues 24,781 23,859 48,640 41,207  
Total operating and interest expenses 16,194 16,455 32,291 31,042  
Equity in earnings (loss) of unconsolidated joint ventures (961) (3,280) 751 (3,743)  
Net operating income (loss) 7,626 4,124 17,100 6,422  
Total assets 2,036,479   2,036,479   1,937,708
Total long-lived assets 1,733,979   1,733,979   1,645,410
Total investments in unconsolidated joint ventures 232,199   232,199   237,321
Corporate & Other [Member]          
Segment Reporting Information [Line Items]          
Total revenues 16 904 (62) 1,577  
Total operating and interest expenses 25,323 29,802 51,696 54,471  
Net operating income (loss) (25,307) $ (28,898) (51,758) $ (52,894)  
Total assets 70,055   70,055   104,531
Total long-lived assets 33,344   33,344   31,901
Total investments in unconsolidated joint ventures $ 298   $ 298   $ 162