Investment in Office Properties and Parking Properties (Details) (USD $)	3 Months Ended		9 Months Ended			0 Months Ended		0 Months Ended		0 Months Ended					0 Months Ended		0 Months Ended	3 Months Ended			0 Months Ended
	Sep. 30, 2014 State	Sep. 30, 2013	Sep. 30, 2014 State	Sep. 30, 2013	Dec. 31, 2013 Office Building Thomas Properties Group, Inc Property	Jan. 30, 2014 Office Building JTB Center Property	Apr. 10, 2014 Office Building Courvoisier Centre Property	Jul. 03, 2014 Office Building Millenia Park One	Sep. 30, 2014 Property Subject to Operating Lease Office Building Property	Apr. 10, 2014 FLORIDA Courvoisier Centre		Apr. 14, 2014 FLORIDA One Orlando Centre	Sep. 19, 2014 Six States Office Building Southern U.S. Office Properties Acquisition	Sep. 19, 2014 Six States Office Building Southern U.S. Office Properties Acquisition Property	Apr. 14, 2014 Hayden Ferry Lakeside III	Sep. 30, 2014 Hayden Ferry Lakeside III	Sep. 04, 2014 Schlumberger Houston, TX	Sep. 30, 2014 Schlumberger Houston, TX	Apr. 14, 2014 First Mortgage FLORIDA One Orlando Centre	Apr. 14, 2014 Second Mortgage FLORIDA One Orlando Centre	Jul. 29, 2014 Mortgage Receivable The Forum at West Paces	Oct. 05, 2014 Subsequent Event Six States Office Building Property	Oct. 05, 2014 Subsequent Event Six States Office Building
Business Acquisition [Line Items]
Number of real estate properties					2	3	2		45					22
Number of states in which office properties located	8		8
Acquisition purchase price						$ 33,300,000		$ 25,500,000		$ 145,800,000	[1]	$ 55,100,000	$ 475,000,000
The Company's Ownership %															70.00%
Cumulative development costs incurred																11,700,000
Investment held in lender reserve to fund leasing and repositioning of the asset												8,000,000
Payments to acquire remaining noncontrolling interest in the borrower			43,502,000	0								1,100,000			2,000,000
Percentage of voting interests acquired												100.00%
Debt assumed in a business combination												68,300,000
Debt instrument face amount																			54,000,000.0	15,300,000
Mortgage note receivable																					50,000,000
Payments to acquire loans receivable			0	3,523,000																	47,000,000
Earnest money deposits														35,000,000
Number of properties under agreement to sell																						19
Gross sales price of assets under agreement to sell																							237,000,000
Net proceeds from sale of real estate																	17,000,000
Proceeds from Sale of Real Estate, Net																	16,200,000
Gains (losses) on sales of real estate	$ 6,664,000	$ 0	$ 6,664,000	$ 0														$ 6,700,000

[1] The purchase price of Courvoisier Centre was reduced by $5.3 million of credits from the seller.