Accounting Policies Accounting Policies (Details 3) - USD ($)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Non-cash changes to balance sheet - Investing Activities
Projects under construction and development	$ 37,022,000	$ (359,234,000)
Completed rental properties	840,553,000	(123,472,000)
Restricted cash	8,969,000	20,000
Notes and accounts receivable	0	42,991,000
Investments in and advances to affiliates - due to dispositions or change in control	71,438,000	97,154,000
Investments in and advances to affiliates - other activity	14,990,000	15,377,000
Total non-cash effect on investing activities	972,972,000	(327,164,000)
Non-cash changes to balance sheet - Financing Activities
Accounts payable, accrued expenses and other liabilities	0	41,828,000
Nonrecourse mortgage debt and notes payable	450,470,000	(339,309,000)
Convertible senior debt	(286,196,000)	0
Class A common stock	4,548,000	225,000
Additional paid-in capital	285,595,000	(33,611,000)
Treasury stock	(6,503,000)	0
Redeemable noncontrolling interest	0	28,390,000
Noncontrolling interest	(585,000)	(34,342,000)
Total non-cash effect on financing activities	$ 447,329,000	$ (336,819,000)