Investment in and Advances to Non-Consolidated Entities (Details) (USD $)	1 Months Ended	6 Months Ended		12 Months Ended	3 Months Ended	6 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended
	Jul. 31, 2012	Jun. 30, 2013 sqft	Jun. 30, 2012	Dec. 31, 2012 Partnerships	Jun. 30, 2012 Concord and CDH CDO [Member]	Jun. 30, 2012 Concord and CDH CDO [Member]	Jun. 30, 2013 Concord and CDH CDO [Member]	Jul. 31, 2012 Financial Standby Letter of Credit [Member]	Mar. 31, 2013 Palm Beach Garden, FL Office [Member] Joint Venture [Member]	Dec. 31, 2012 Palm Beach Garden, FL Office [Member] Joint Venture [Member] sqft	Jun. 30, 2013 Palm Beach Garden, FL Office [Member] Joint Venture [Member]	Dec. 31, 2012 Humble Texas [Member] Joint Venture [Member]	Dec. 31, 2012 Nonrecourse Mortgage [Member] Humble Texas [Member] Joint Venture [Member]
Investments in and Advances to Affiliates [Line Items]
Equity Method Investment, Number of Joint Venture Formed During Period				2
Square feet of property		1,163,000								120,000
Investment in joint venture		$ 0	$ 1,920,000							$ 29,750,000
Equity Method Investment, Ownership Percentage										36.00%	25.00%	15.00%
Lease Term (Years)										15 years		17 years
Advances to Affiliate										12,000,000
Distributions Payable to Real Estate Partnerships									2,557,000
Economic Interest in Joint Venture				100.00%
Property Purchase Price												27,750,000
Debt Instrument, Face Amount													15,260,000
Debt Instrument, Interest Rate, Stated Percentage													4.70%
Proceeds from Divestiture of Interest in Consolidated Subsidiaries	13,218,000
Guarantor Obligations, Contingent Letter of Credit								2,500,000
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest							0
Equity Method Investment distributions						885,000
Equity Method Investment Sold, Carrying Amount					$ 7,000,000