Reportable Segments (Revenue Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Rental property operating expenses	$ (155,934)	$ (90,498)	$ (50,329)
Total consolidated revenues	361,383	210,741	136,846
Total
Segment Reporting Information [Line Items]
Net operating income	215,673	138,080	110,457
Sales less cost of sales	3,910	1,464	5,224
Fee income	12,519	10,967	34,162
Other income	5,404	3,528	5,153
Rental property operating expenses	155,934	90,498	50,329
Cost of sales	325	1,753	1,833
Net operating income in joint ventures	(25,896)	(27,763)	(23,956)
Sales less cost of sales in joint ventures	(2,207)	(111)	(28)
Net operating income in discontinued operations	(1,800)	(6,390)	(22,983)
Fee income in discontinued operations	0	(76)	(16,364)
Other income in discontinued operations	(565)	(64)	(3,622)
Termination Fees in Discontinues Operations and in Joint Ventures	(187)	0	0
Gain on land sales (included in gain on investment properties)	(1,727)	(1,145)	(3,719)
Total consolidated revenues	$ 361,383	$ 210,741	$ 136,486