Acquisitions, Dispositions, and Mortgage Funding (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues
Other operating	$ 1,456	$ 1,774
Revenues	82,584	76,165
Expenses
Property operating	29,826	28,285
General and administrative	6,541	5,261
Depreciation	21,852	20,479
Amortization	2,689	2,522
Bad debt, net of recoveries	(12)	(41)
Total Expenses	60,896	56,506
Other Income (Expense)
Interest and other income, net	232	216
Total other income (expense)	(19,563)	(18,163)
Discontinued Operations
Income from discontinued operations	487	2,380
Impairments	(3,630)	(4,170)
Gain on sales of real estate properties	0	3,428
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	(3,143)	1,638
Discontinued Operations [Member]
Revenues
Rental income	851	4,292
Other operating	0	5
Revenues	851	4,297
Expenses
Property operating	316	1,104
General and administrative	0	5
Depreciation	48	909
Amortization	0	15
Bad debt, net of recoveries	0	(1)
Total Expenses	364	2,032
Other Income (Expense)
Interest and other income, net	0	115
Total other income (expense)	0	115
Discontinued Operations
Income from discontinued operations	487	2,380
Impairments	(3,630)	(4,170)
Gain on sales of real estate properties	0	3,428
INCOME (LOSS) FROM DISCONTINUED OPERATIONS	$ (3,143)	$ 1,638