Organization (Details) (USD $)	6 Months Ended												60 Months Ended				3 Months Ended
	Jun. 30, 2013 Y acre Vehicles sqft	Jun. 30, 2012	Jun. 30, 2013 Commercial Real Estate Properties [Member] sqft Real_Estate_Properties	Jun. 30, 2013 Total Properties Under Construction [ Member] Real_Estate_Properties sqft	Jun. 30, 2013 Total Office Properties [ Member] Real_Estate_Properties	Jun. 30, 2013 Class A Office Properties [Member] Real_Estate_Properties	Jun. 30, 2013 Office Properties Under Construction [ Member] Real_Estate_Properties	Jun. 30, 2013 Office Technical Properties [Member] Real_Estate_Properties	Jun. 30, 2013 Hotel Property [ Member] Real_Estate_Properties	Jun. 30, 2013 Retail Properties [ Member] Real_Estate_Properties	Jun. 30, 2013 Residential Properties [Member] Real_Estate_Properties	Jun. 30, 2013 Residential Properties Under Construction [Member] Real_Estate_Properties	Mar. 26, 2018 Series B Cumulative Redeemable Preferred Stock [Member]	Jun. 30, 2013 Series B Cumulative Redeemable Preferred Stock [Member]	Dec. 31, 2012 Series B Cumulative Redeemable Preferred Stock [Member]	Jun. 30, 2013 Depository shares of Series B Cumulative Redeemable Preferred [Member]	Jun. 30, 2013 Series Two Preferred Units [Member]	Jun. 30, 2013 series four preferred units [Member]	Aug. 07, 2013 series four preferred units [Member]	Jun. 30, 2013 Series B Preferred Units [Member]
Real Estate Properties [Line Items]
General and limited partnership interest in the operating partnership (percent)	89.20%	88.50%
Restriction on redemption of OP units from date of issuance (years)	1
One OP unit is equivalent to one share of Common Stock (in shares)	1
OP unit conversion rate (in shares)	1
Series B, Shares Outstanding														80,000	0	8,000,000				80,000
Series B, Dividend Rate, Percentage													5.25%
Number Of Series Of Preferred Units Outstanding	3
OP Units for each Preferred Unit (in shares)																	1.312336
Preferred Units Liquidation Preference																	$ 50.00	$ 50.00	$ 50.00
Quarterly Distributions to Series Four Preferred Units																		$ 0.25
Series Four Preferred Units Annual Dividend Payable Rate																		2.00%
Number of real estate properties			179	8	171	131	7	40	1	4	3	1
Net Rentable Area			44,800,000	2,800,000
Number of vehicles in structured parking	46,411
Area of parking (in square feet)	15,700,000
Area of undeveloped land parcels owned (in acres)	512.8