Acquisitions, Dispositions and Other Significant Transactions (Details Textual) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) Units Property	Sep. 30, 2015 USD ($) Units Property	Sep. 30, 2016 USD ($) Units Property	Sep. 30, 2015 USD ($) Units Property	Dec. 31, 2015 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income before income taxes and gain on disposition	$ 15,538	$ 23,769	$ 68,648	$ 66,133
Net (income) loss attributable to noncontrolling interests in consolidated real estate partnerships	(12,489)	$ 785	(22,096)	$ (4,082)
Assets	6,293,847		6,293,847		$ 6,118,681
Liabilities	4,363,039		4,363,039		4,266,850
Noncontrolling interests in consolidated real estate partnerships	$ 150,086		$ 150,086		$ 151,365
Indigo Apartment Homes - Redwood City CA [Member] [Domain]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of apartment homes in apartment communities | Units	463		463
Payments to acquire and develop real estate			$ 303,000
Portion of payments to acquire real estate placed in escrow to be released to seller upon completion of construction project			11,100
Preferred units issued during period, value			$ 17,000
Per annum distribution rate			6.00%
Capitalized asset acquisition costs			$ 1,800
Total fair value allocated to land	$ 93,000		93,000
Total fair value allocated to buildings and improvements	226,800		226,800
Total fair value allocated to furniture and fixtures	2,000		2,000
Class Z Cumulative Preferred Stock [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Preferred stock redemption amount	$ 34,800		34,800
Preferred stock redemption premium			700
Previously deferred issuance costs reflected as an adjustment of net income attributable to preferred equity holders			$ 1,300
Wholly And Partially Owned Consolidated Properties [Member] | Assets Held-for-sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of apartment homes in apartment communities | Units	1,402		1,402
Number of Apartment Communities | Property	4		4
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | Wholly And Partially Owned Consolidated Properties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Apartment communities sold | Property	1	0	4	8
Apartment homes sold | Units	296	0	1,939	2,891
Income before income taxes and gain on disposition	$ 78	$ 398	$ 1,619	$ 2,845
Prepayment penalties incurred upon repayment of debt collateralized by apartment communities sold				19,800
Mark-to-market adjustment included in prepayment penalties				$ 13,200
Napico Portfolio [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Apartment Communities | Property	2		2
Decrease in other assets from deconsolidation			$ 105,400
Decrease in accrued liabilities and other from deconsolidation			111,600
Other nonrecurring gain			5,000
Net (income) loss attributable to noncontrolling interests in consolidated real estate partnerships			(7,800)
Assets	$ 36,500		36,500
Liabilities	41,700		41,700
Noncontrolling interests in consolidated real estate partnerships	$ 100		$ 100