Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Series G Preferred Units	Dec. 31, 2012 Series G Preferred Units	Jun. 30, 2013 Series H Preferred Units	Dec. 31, 2012 Series H Preferred Units	Dec. 31, 2012 Series C Preferred Stock	Jun. 30, 2013 Series I Preferred Stock	Dec. 31, 2012 Series I Preferred Stock
Tenant and other receivables, allowance (in dollars)	$ 20,466	$ 21,652
Deferred rents receivable, allowance (in dollars)	29,821	29,580
Debt and preferred equity investments, discount and deferred origination fees (in dollars)	27,107	22,341
Debt and preferred equity investments, allowance (in dollars)	$ 7,000	$ 7,000
Preferred Units, liquidation preference (in dollars per share)			$ 25.00	$ 25.00	$ 25.00	$ 25.00
Preferred Units, shares issued			1,902,000	1,902,000	80,000	80,000
Preferred Units, shares outstanding			1,902,000	1,902,000	80,000	80,000
Preferred stock, par value (in dollars per share)	$ 0.01						$ 0.01	$ 0.01	$ 0.01
Preferred stock, liquidation preference (in dollars per share)							$ 25.00	$ 25.00	$ 25.00
Preferred stock, shares issued							7,700,000	9,200,000	9,200,000
Preferred stock, shares outstanding							7,700,000	9,200,000	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	95,376,000	94,896,000
Common stock, shares outstanding	95,376,000	94,896,000
Treasury stock, shares	3,563,000	3,646,000