Disposals and Other Significant Transactions (Details 1) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) Units Property	Mar. 31, 2015 USD ($) Units Property
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
(Loss) income before income taxes and gain on disposition	$ 23,698	$ 18,457
Gain on dispositions of real estate, net of tax	$ 6,187	$ 85,693
Wholly And Partially Owned Consolidated Properties [Member] | Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Apartment communities sold | Property	1	6
Apartment homes sold | Units	96	1,100
(Loss) income before income taxes and gain on disposition	$ (36)	$ 278
Gain on dispositions of real estate, net of tax	6,187	85,693
Income tax related to gain on disposition of real estate	195	0
Prepayment penalties incurred upon repayment of debt collateralized by apartment communities sold	0	12,135
Mark-to-market adjustment included in prepayment penalties	$ 0	$ 7,705