Business Segments - (Details 1) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Total assets	$ 6,097,028		$ 6,079,413
Operating Segments [Member] | Conventional Real Estate [Member]
Segment Reporting Information [Line Items]
Total assets	5,116,474		4,815,063
Operating Segments [Member] | Affordable Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total assets	480,499		535,857
Proportionate Adjustments [Member]
Segment Reporting Information [Line Items]
Total assets	65,139	[1]	253,019	[1]
Corporate Nonsegment And Other Reconciling Items Member [Member]
Segment Reporting Information [Line Items]
Total assets	$ 434,916		$ 475,474

[1] Represents adjustments for the noncontrolling interests in consolidated real estate partnerships’ share of the assets of our consolidated apartment communities, which are excluded from our measurement of segment financial condition, and our share of the assets of our unconsolidated real estate partnerships, which are included in our measure of segment financial condition.