Capital and Financing Transactions - Summary of Mortgage Notes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended	12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		0 Months Ended	12 Months Ended			12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended				12 Months Ended				12 Months Ended				12 Months Ended		12 Months Ended		12 Months Ended						12 Months Ended					12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Mar. 09, 2012	Nov. 15, 2012 Westshore Corporate Center [Member]	Dec. 31, 2013 Westshore Corporate Center [Member]	Dec. 31, 2012 Westshore Corporate Center [Member]	Dec. 31, 2013 Teachers Insurance and Annuity Association [Member]	Dec. 31, 2012 Teachers Insurance and Annuity Association [Member]	Dec. 31, 2013 NASCAR Plaza [Member]	Dec. 31, 2012 NASCAR Plaza [Member]	Dec. 31, 2013 John Hancock Facility [Member]	Dec. 31, 2012 John Hancock Facility [Member]	Dec. 31, 2013 Capital City Plaza [Member]	Dec. 31, 2012 Capital City Plaza [Member]	Jan. 09, 2012 The Pointe [Member]	Dec. 31, 2013 The Pointe [Member]	Dec. 31, 2012 The Pointe [Member]	Jan. 11, 2012 The Pointe [Member]	Dec. 31, 2013 Corporate Center Four at International Plaza [Member]		Dec. 31, 2012 Corporate Center Four at International Plaza [Member]		Dec. 31, 2013 Morgan Keegan Tower [Member]	Dec. 31, 2012 Morgan Keegan Tower [Member]	Dec. 31, 2013 Citrus Center [Member]	Dec. 31, 2012 Citrus Center [Member]	Dec. 31, 2013 Bank of America Center		Dec. 31, 2012 Bank of America Center		Dec. 31, 2013 Stein Mart [Member]	Dec. 31, 2012 Stein Mart [Member]	Dec. 31, 2013 Phoenix Tower [Member]	Dec. 31, 2012 Phoenix Tower [Member]	Dec. 31, 2013 Deerwood [Member]	Dec. 31, 2012 Deerwood [Member]	Dec. 31, 2013 Lincoln Place	Dec. 31, 2012 Lincoln Place	Dec. 31, 2013 CityWestPlace I and II [Member]	Dec. 31, 2012 CityWestPlace I and II [Member]	Dec. 31, 2013 CityWestPlace III and IV [Member]	Dec. 31, 2012 CityWestPlace III and IV [Member]	Dec. 31, 2013 San Felipe Plaza [Member]	Dec. 31, 2012 San Felipe Plaza [Member]	Dec. 31, 2013 Wholly Owned Properties [Member]	Dec. 31, 2012 Wholly Owned Properties [Member]	Dec. 31, 2013 Partially Owned Properties [Member]	Dec. 31, 2012 Partially Owned Properties [Member]	Dec. 31, 2013 Subsidiaries [Member] The Pointe [Member]	Dec. 31, 2012 Subsidiaries [Member] The Pointe [Member]	Dec. 31, 2013 Subsidiaries [Member] 245 Riverside [Member]		Dec. 31, 2012 Subsidiaries [Member] 245 Riverside [Member]		Dec. 31, 2013 Subsidiaries [Member] Corporate Center Four at International Plaza [Member]		Dec. 31, 2012 Subsidiaries [Member] Corporate Center Four at International Plaza [Member]		Dec. 31, 2013 Subsidiaries [Member] Bank of America Center		Dec. 31, 2012 Subsidiaries [Member] Bank of America Center		Dec. 31, 2013 Subsidiaries [Member] Cypress Center I - III [Member]	Dec. 31, 2012 Subsidiaries [Member] Cypress Center I - III [Member]	Dec. 31, 2013 Subsidiaries [Member] 3344 Peachtree [Member]	Dec. 31, 2012 Subsidiaries [Member] 3344 Peachtree [Member]	Dec. 31, 2013 Subsidiaries [Member] Hayden Ferry Lakeside I [Member]		Dec. 31, 2013 Subsidiaries [Member] Hayden Ferry Lakeside II [Member]		Dec. 31, 2012 Subsidiaries [Member] Hayden Ferry Lakeside II [Member]		Dec. 31, 2013 Subsidiaries [Member] Two Ravinia [Member]		Dec. 31, 2013 Subsidiaries [Member] Two Liberty Place [Member]	Dec. 31, 2013 Subsidiaries [Member] Carmel Crossing [Member]	Dec. 31, 2012 Subsidiaries [Member] Carmel Crossing [Member]	Dec. 31, 2013 Parkway Properties [Member]	Dec. 31, 2012 Parkway Properties [Member]
Debt Instrument [Line Items]
Fixed rate (in percent)			7.10%	2.50%	2.50%		6.20%		3.40%	3.40%	7.60%		7.30%			4.00%		4.00%	4.60%	[1]			7.60%		6.30%		4.70%	[2]			6.50%		3.90%		3.90%		3.60%		6.20%		5.00%		4.80%						4.00%		5.20%	[1]			5.40%	[1]			4.70%	[1],[2]			4.10%		5.30%		4.50%	[1]	5.00%	[1]			5.00%	[1]	5.20%	5.50%
Maturity Date				May 01, 2015	May 01, 2015		Jan. 01, 2016		Mar. 30, 2016	Mar. 30, 2016	Jun. 01, 2016		Mar. 05, 2017		Feb. 10, 2019	Feb. 10, 2019			Apr. 08, 2019	[1]			Oct. 01, 2019		Jun. 01, 2020		May 18, 2018	[2]			Aug. 01, 2020		Mar. 01, 2023		Apr. 01, 2023		Jun. 11, 2016		Jul. 06, 2016		Mar. 05, 2020		Dec. 01, 2018						Feb. 10, 2019		Mar. 31, 2019	[1]			Apr. 08, 2019	[1]			May 18, 2018	[1],[2]			May 18, 2016		Oct. 01, 2017		Jul. 25, 2018	[1]	Jul. 25, 2018	[1]			May 20, 2019	[1]	Jun. 10, 2019	Mar. 10, 2020
Monthly Payment					$ 88		$ 565		$ 0		$ 130		$ 253			$ 79			$ 143	[1]			$ 163		$ 153		$ 138	[2]			$ 81		$ 258		$ 276		$ 293		$ 738		$ 512		$ 438		$ 4,308		$ 1,288		$ 0		$ 42	[1]			$ 0	[1]			$ 0	[1],[2]			$ 0		$ 485		$ 85	[1]	$ 190	[1]			$ 95	[1]	$ 391	$ 0		$ 11,192
Note Balance	1,081,597				14,312	14,520	71,307	73,584	0	42,608	17,634	17,852	32,860	33,489		23,500	0	23,500	36,000	[1]	0	[1]	9,211	10,419	21,601	22,035	33,875	[2]	0	[2]	11,286	11,517	80,000	0	84,500	0	49,317	0	117,663	0	93,367	0	110,000	0	806,433	226,024	275,164	380,125	0	23,500	9,250	[1]	9,250	[1]	0	[1]	22,500	[1]	0	[1],[2]	33,875	[1],[2]	0	12,088	84,739	86,487	22,000	[1]	46,875	[1]	48,125	[1]	22,100	[1]	90,200	0	10,000	1,097,493	605,889
Periodic unamortized premium (discount)	5,596
Unamortized premium (discount)	$ 15,896	$ (260)

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

[2] 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.