Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Series H Preferred Units	Dec. 31, 2011 Series H Preferred Units	Dec. 31, 2012 Series G Preferred Units	Dec. 31, 2012 Series C Preferred Stock	Dec. 31, 2011 Series C Preferred Stock	Dec. 31, 2012 Series D Preferred Stock	Dec. 31, 2011 Series D Preferred Stock	Dec. 31, 2012 Series I Preferred Stock
Tenant and other receivables, allowance (in dollars)	$ 21,652	$ 16,772
Deferred rents receivable, allowance (in dollars)	29,580	29,156
Debt and preferred equity investments, discount (in dollars)	13,572	24,996
Debt and preferred equity investments, allowance (in dollars)	$ 7,000	$ 50,175
Preferred Units, par value (in dollars per share)			$ 0.01	$ 0.01	$ 0.01
Preferred Units, shares issued			80,000	80,000	1,902,000
Preferred Units, shares outstanding			80,000	80,000	1,902,000
Preferred Units, liquidation preference (in dollars per share)			$ 25.00	$ 25.00	$ 25.00
Preferred stock, par value (in dollars per share)	$ 0.01					$ 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	$ 25.00
Preferred stock, shares issued						7,700,000	11,700,000	0	4,000,000	9,200,000
Preferred stock, shares outstanding						7,700,000	11,700,000	0	4,000,000	9,200,000
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	94,896,000	89,210,000
Common stock, shares outstanding	94,896,000	89,210,000
Treasury stock, shares	3,646,000	3,427,000