Capital and Financing Transactions - Summary Schedule of Mortgage Notes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended					12 Months Ended					0 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2014		Dec. 23, 2013
Debt Instrument [Line Items]
Note Balance	$ 1,311,608					$ 1,311,608					$ 1,311,608
Unamortized premium (discount)	27,842					27,842		15,896			27,842
Loss on extinguishment of debt	2,066		0	339	0	2,405		0		0
Westshore Corporate Center
Debt Instrument [Line Items]
Fixed rate (in percent)	2.50%	[1]				2.50%	[1]				2.50%	[1]
Maturity Date						May 01, 2015
Monthly Payment						88
Note Balance	14,091					14,091		14,312			14,091
Teachers Insurance and Annuity Associations (5 properties)
Debt Instrument [Line Items]
Fixed rate (in percent)	6.20%	[1]				6.20%	[1]				6.20%	[1]
Maturity Date						Jan. 01, 2016
Monthly Payment						565
Note Balance	68,884					68,884		71,307			68,884
John Hancock Facility (2 properties)
Debt Instrument [Line Items]
Fixed rate (in percent)	7.60%	[1]				7.60%	[1]				7.60%	[1]
Maturity Date						Jun. 01, 2016
Monthly Payment						130
Note Balance	17,398					17,398		17,634			17,398
3350 Peachtree, formerly Capital City Plaza
Debt Instrument [Line Items]
Fixed rate (in percent)	7.30%	[1]				7.30%	[1]				7.30%	[1]
Maturity Date						Mar. 05, 2017
Monthly Payment						253
Note Balance	32,185					32,185		32,860			32,185
One Orlando Centre
Debt Instrument [Line Items]
Fixed rate (in percent)	4.60%	[1]				4.60%	[1]				4.60%	[1]
Maturity Date						May 11, 2017
Monthly Payment						265
Note Balance	54,000					54,000		0			54,000
One Congress Plaza
Debt Instrument [Line Items]
Fixed rate (in percent)	3.20%	[1]				3.20%	[1]				3.20%	[1]
Maturity Date						Jun. 11, 2017
Monthly Payment						649
Note Balance	128,000					128,000		0			128,000
San Jacinto Center
Debt Instrument [Line Items]
Fixed rate (in percent)	3.20%	[1]				3.20%	[1]				3.20%	[1]
Maturity Date						Jun. 11, 2017
Monthly Payment						509
Note Balance	101,000					101,000		0			101,000
The Pointe
Debt Instrument [Line Items]
Fixed rate (in percent)	4.00%	[1]				4.00%	[1]				4.00%	[1]
Maturity Date						Feb. 10, 2019
Monthly Payment						78
Note Balance	23,500					23,500		23,500			23,500
Corporate Center IV
Debt Instrument [Line Items]
Fixed rate (in percent)	4.60%	[1],[2]				4.60%	[1],[2]				4.60%	[1],[2]
Maturity Date						Apr. 08, 2019	[2]
Monthly Payment						129	[2]
Note Balance	36,000	[2]				36,000	[2]	36,000	[2]		36,000	[2]
Raymond James Tower
Debt Instrument [Line Items]
Fixed rate (in percent)	7.60%	[1],[3]				7.60%	[1],[3]				7.60%	[1],[3]
Maturity Date						Oct. 01, 2019	[3]
Monthly Payment						0	[3]
Note Balance	0	[3]				0	[3]	9,211	[3]		0	[3]
Citrus Center
Debt Instrument [Line Items]
Fixed rate (in percent)	6.30%	[1]				6.30%	[1]				6.30%	[1]
Maturity Date						Jun. 01, 2020
Monthly Payment						153
Note Balance	21,138					21,138		21,601			21,138
Bank of America Center
Debt Instrument [Line Items]
Fixed rate (in percent)	4.70%	[1],[4]				4.70%	[1],[4]				4.70%	[1],[4]
Maturity Date						May 18, 2018	[4]
Monthly Payment						0	[4]
Note Balance	0	[4]				0	[4]	33,875	[4]		0	[4]
Stein Mart
Debt Instrument [Line Items]
Fixed rate (in percent)	6.50%	[1]				6.50%	[1]				6.50%	[1]
Maturity Date						Aug. 01, 2020
Monthly Payment						81
Note Balance	11,041					11,041		11,286			11,041
Phoenix Tower
Debt Instrument [Line Items]
Fixed rate (in percent)	3.90%	[1]				3.90%	[1]				3.90%	[1]
Maturity Date						Mar. 01, 2023
Monthly Payment						258
Note Balance	80,000					80,000		80,000			80,000
Deerwood North and South
Debt Instrument [Line Items]
Fixed rate (in percent)	3.90%	[1]				3.90%	[1]				3.90%	[1]
Maturity Date						Apr. 01, 2023
Monthly Payment						276
Note Balance	84,500					84,500		84,500			84,500
Lincoln Place
Debt Instrument [Line Items]
Fixed rate (in percent)	3.60%	[1]				3.60%	[1]				3.60%	[1]
Maturity Date						Jun. 11, 2016
Monthly Payment						293
Note Balance	48,670					48,670		49,317			48,670
CityWestPlace I & II
Debt Instrument [Line Items]
Fixed rate (in percent)	3.50%	[1]				3.50%	[1]				3.50%	[1]
Maturity Date						Jul. 06, 2016
Monthly Payment						738
Note Balance	116,111					116,111		117,663			116,111
CityWestPlace III & IV
Debt Instrument [Line Items]
Fixed rate (in percent)	4.30%	[1]				4.30%	[1]				4.30%	[1]
Maturity Date						Mar. 05, 2020
Monthly Payment						512
Note Balance	91,889					91,889		93,367			91,889
San Felipe Plaza
Debt Instrument [Line Items]
Fixed rate (in percent)	4.30%	[1]				4.30%	[1]				4.30%	[1]
Maturity Date						Dec. 01, 2018
Monthly Payment						576
Note Balance	109,585					109,585		110,000			109,585
Total Wholly Owned
Debt Instrument [Line Items]
Monthly Payment						5,553
Note Balance	1,037,992					1,037,992		806,433			1,037,992
Total Fund II
Debt Instrument [Line Items]
Monthly Payment						1,289
Note Balance	273,616					273,616		275,164			273,616
Subsidiaries | 3344 Peachtree
Debt Instrument [Line Items]
Fixed rate (in percent)	5.30%	[1]				5.30%	[1]				5.30%	[1]
Maturity Date						Oct. 01, 2017
Monthly Payment						485
Note Balance	82,907					82,907		84,739			82,907
Subsidiaries | Hayden Ferry Lakeside I
Debt Instrument [Line Items]
Fixed rate (in percent)	4.50%	[1],[2]				4.50%	[1],[2]				4.50%	[1],[2]
Maturity Date						Jul. 25, 2018	[2]
Monthly Payment						112	[2]
Note Balance	21,887	[2]				21,887	[2]	22,000	[2]		21,887	[2]
Subsidiaries | Hayden Ferry Lakeside II
Debt Instrument [Line Items]
Fixed rate (in percent)	4.50%	[1],[2]				4.50%	[1],[2]				4.50%	[1],[2]
Maturity Date						Jul. 25, 2018	[2]
Monthly Payment						163	[2]
Note Balance	46,875	[2]				46,875	[2]	46,875	[2]		46,875	[2]
Subsidiaries | Hayden Ferry Lakeside III
Debt Instrument [Line Items]
Variable rate (in percent)	2.00%					2.00%					2.00%
Maturity Date						Jul. 25, 2018
Monthly Payment						1
Note Balance	481					481		0			481
Subsidiaries | 245 Riverside
Debt Instrument [Line Items]
Fixed rate (in percent)	5.20%	[1],[2]				5.20%	[1],[2]				5.20%	[1],[2]
Maturity Date						Mar. 31, 2019	[2]
Monthly Payment						51	[2]
Note Balance	9,166	[2]				9,166	[2]	9,250	[2]		9,166	[2]
Subsidiaries | Two Ravinia
Debt Instrument [Line Items]
Fixed rate (in percent)	5.00%	[1],[2]				5.00%	[1],[2]				5.00%	[1],[2]
Maturity Date						May 20, 2019	[2]
Monthly Payment						86	[2]
Note Balance	22,100	[2]				22,100	[2]	22,100	[2]		22,100	[2]
Subsidiaries | Two Liberty Place
Debt Instrument [Line Items]
Fixed rate (in percent)	5.20%					5.20%					5.20%
Maturity Date						Jun. 10, 2019
Monthly Payment						391
Note Balance	90,200					90,200		90,200			90,200
Parkway Properties
Debt Instrument [Line Items]
Monthly Payment						6,842
Note Balance	1,339,450					1,339,450		1,097,493			1,339,450
Bank of America Center
Debt Instrument [Line Items]
Ownership interest acquired (in percent)													70.00%
Mortgages | Raymond James Tower
Debt Instrument [Line Items]
Loss on extinguishment of debt											$ 2,100

[1] This represents the net effective interest rate.

[2] Property has entered into an interest rate swap agreement with the Lender associated with these mortgage loans.

[3] The first mortgage secured by Raymond James Tower was prepaid in full on December 31, 2014, and the asset was sold on January 15, 2015. The Company incurred a $2.1 million loss on extinguishment of debt as a result of the debt prepayment.

[4] On December 23, 2013, the Company acquired its partner's 70.0% ownership interest in Bank of America Center. No changes were made to the size, structure or terms of the mortgage note secured by the property.