Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Series C Preferred Stock	Dec. 31, 2011 Series C Preferred Stock	Nov. 30, 2011 Series C Preferred Stock	Jun. 30, 2012 Series D Preferred Stock	Dec. 31, 2011 Series D Preferred Stock	Jun. 30, 2012 Series H Preferred Units	Dec. 31, 2011 Series H Preferred Units	Jun. 30, 2012 Series G Preferred Units
Tenant and other receivables, allowance (in dollars)	$ 20,826	$ 16,772
Deferred rents receivable, allowance (in dollars)	31,343	29,156
Debt and preferred equity investments, discount (in dollars)	22,601	24,996
Debt and preferred equity investments, allowance (in dollars)	$ 41,050	$ 50,175
Preferred units, liquidation preference (in dollars per share)					$ 25.00			$ 25.00	$ 25.00	$ 25.00
Preferred units, shares issued					80,000			80,000	80,000	1,902,000
Preferred Units, shares outstanding								80,000	80,000	1,902,000
Preferred stock, par value (in dollars per share)	$ 0.01		$ 0.01	$ 0.01		$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)			$ 25.00	$ 25.00		$ 25.00	$ 25.00
Preferred stock, shares issued			11,700,000	11,700,000		4,000,000	4,000,000
Preferred stock, shares outstanding			11,700,000	11,700,000		4,000,000	4,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	93,543,000	89,210,000
Common stock, shares outstanding	93,543,000	89,210,000
Treasury stock, shares	3,605,000	3,427,000