Organization (Details) (USD $)	3 Months Ended											3 Months Ended		3 Months Ended
	Mar. 31, 2014 Y sqft Vehicles acre	Mar. 31, 2013	Mar. 31, 2014 Commercial Real Estate Properties [Member] Real_Estate_Properties sqft	Mar. 31, 2014 Total Properties Under Construction [ Member] Real_Estate_Properties sqft	Mar. 31, 2014 Total Office Properties [ Member] Real_Estate_Properties	Mar. 31, 2014 Class A Office Properties [Member] Real_Estate_Properties	Mar. 31, 2014 Office Properties Under Construction [ Member] Real_Estate_Properties	Mar. 31, 2014 Office Technical Properties [Member] Real_Estate_Properties	Mar. 31, 2014 Hotel Property [ Member] Real_Estate_Properties	Mar. 31, 2014 Retail Properties [ Member] Real_Estate_Properties	Mar. 31, 2014 Residential Properties [Member] Real_Estate_Properties	Mar. 31, 2014 Series B Cumulative Redeemable Preferred Stock [Member]	Dec. 31, 2013 Series B Cumulative Redeemable Preferred Stock [Member]	Mar. 31, 2014 Series Two Preferred Units [Member]	Mar. 31, 2014 series four preferred units [Member]	Mar. 31, 2014 Series B Preferred Units [Member]	Mar. 31, 2014 depositary shares [Member] Series B Cumulative Redeemable Preferred Stock [Member]
Real Estate Properties [Line Items]
Ratio of depository shares to shares of Series B Preferred Stock												0.01
General and limited partnership interest in the operating partnership (percent)	89.50%	89.00%
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	80,000			80,000	8,000,000
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
Quarterly Distributions to Series Four Preferred Units															$ 0.25
Series Four Preferred Units Annual Dividend Payable Rate															2.00%
Number of real estate properties			175	8	167	128	8	39	1	4	3
Net Rentable Area			45,800,000	4,000,000
Number of vehicles in structured parking	45,971
Area of parking (in square feet)	15,700,000
Area of undeveloped land parcels owned (in acres)	502.5