Acquisitions, Dispositions and Other Significant Transactions (Details 1) $ 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
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
Gain on dispositions of real estate, net of tax	$ 14,498	$ 0	$ 237,226	$ 130,474
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 | Property	1	0	4	8
Apartment homes | Units	296	0	1,939	2,891
Income before income taxes and gain on disposition	$ 78	$ 398	$ 1,619	$ 2,845
Gain on dispositions of real estate, net of tax	$ 14,498	$ 0	$ 237,226	$ 130,474