Investment in Unconsolidated Joint Ventures (Details) $ in Thousands		3 Months Ended
		Mar. 31, 2016 USD ($) ft²	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Document Period End Date		Mar. 31, 2016
Document Fiscal Year Focus		2016
SUMMARY OF FINANCIAL POSITION:
Total Assets		$ 663,350		$ 644,880
Total Debt		398,363		401,977
Total Equity		240,464		219,079
Company's Investment		87,950		79,434
SUMMARY OF OPERATIONS:
Total Revenues		26,307	$ 24,757
Net Income (Loss)		5,332	5,625
Income (Loss) from Equity Method Investments Gross of Impairment Charges		$ 1,834	1,611
Area of Real Estate Property | ft²		129,000
Terminus Office Holdings [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		$ 277,093		277,444
Total Debt		210,590		211,216
Total Equity		54,397		56,369
Company's Investment		28,067		29,110
SUMMARY OF OPERATIONS:
Total Revenues		10,431	9,802
Net Income (Loss)		1,028	987
Income (Loss) from Equity Method Investments Gross of Impairment Charges		514	369
EP I LLC [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		82,033		83,115
Total Debt		58,030		58,029
Total Equity		22,639		24,172
Company's Investment		20,885		21,502
SUMMARY OF OPERATIONS:
Total Revenues		3,003	3,176
Net Income (Loss)		650	735
Income (Loss) from Equity Method Investments Gross of Impairment Charges		462	551
EP II LLC [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		68,901		70,704
Total Debt		42,964		40,910
Total Equity		23,612		24,331
Company's Investment		18,657		19,118
SUMMARY OF OPERATIONS:
Total Revenues		899	0
Net Income (Loss)		(618)	30
Income (Loss) from Equity Method Investments Gross of Impairment Charges		(450)	(9)
Charlotte Gateway Village, LLC [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		121,858		123,531
Total Debt		12,854		17,536
Total Equity		107,381		104,336
Company's Investment		11,288		11,190
SUMMARY OF OPERATIONS:
Total Revenues		8,482	8,442
Net Income (Loss)		3,348	3,077
Income (Loss) from Equity Method Investments Gross of Impairment Charges		536	303
HICO Victory Center LP [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		13,612		13,532
Total Debt		0		0
Total Equity		13,569		13,229
Company's Investment		9,316		9,138
SUMMARY OF OPERATIONS:
Total Revenues		82	0
Net Income (Loss)		75	0
Income (Loss) from Equity Method Investments Gross of Impairment Charges		38	0
Temco Associates, LLC [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		5,295		5,284
Total Debt		0		0
Total Equity		5,181		5,133
Company's Investment		1,066		977
SUMMARY OF OPERATIONS:
Total Revenues		206	58
Net Income (Loss)		170	(1)
Income (Loss) from Equity Method Investments Gross of Impairment Charges		88	(2)
Carolina Square Holdings LP [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		26,702		15,729
Total Debt		0		0
Total Equity		21,385		12,085
Company's Investment		11,486		6,782
CL Realty, L.L.C. [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		7,761		7,872
Total Debt		0		0
Total Equity		7,709		7,662
Company's Investment		3,546		3,515
SUMMARY OF OPERATIONS:
Total Revenues		133	279
Net Income (Loss)		47	160
Income (Loss) from Equity Method Investments Gross of Impairment Charges		30	69
Wildwood Associates
SUMMARY OF FINANCIAL POSITION:
Total Assets		16,394		16,419
Total Debt		0		0
Total Equity		16,326		16,354
Company's Investment	[1]		(1,136)	(1,122)
SUMMARY OF OPERATIONS:
Total Revenues		0	0
Net Income (Loss)		(28)	(30)
Income (Loss) from Equity Method Investments Gross of Impairment Charges		(14)	(15)
Crawford Long CPI LLC [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		29,307		29,143
Total Debt		73,925		74,286
Total Equity		(46,116)		(46,238)
Company's Investment	[1]	(21,960)		(22,021)
SUMMARY OF OPERATIONS:
Total Revenues		3,071	3,000
Net Income (Loss)		660	680
Income (Loss) from Equity Method Investments Gross of Impairment Charges		330	345
Other Equity Method Investee [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		1,134		2,107
Total Debt		0		0
Total Equity		1,121		1,646
Company's Investment		0		1,245
SUMMARY OF OPERATIONS:
Total Revenues		0	0
Net Income (Loss)		0	(13)
Income (Loss) from Equity Method Investments Gross of Impairment Charges		300	$ 0
DC Charlotte Plaza LLLP [Member]
SUMMARY OF FINANCIAL POSITION:
Total Assets		13,260		0
Total Debt		0		0
Total Equity		13,260		0
Company's Investment		$ 6,735		$ 0
Dimensional Fund Advisors [Member] | DC Charlotte Plaza LLLP [Member]
Schedule of Equity Method Investments [Line Items]
Ownership Percentage of Partner in Joint Venture		5000.00%
DC Charlotte Plaza LLLP [Member]
SUMMARY OF OPERATIONS:
Area of Real Estate Property | ft²		229,000

[1] Negative balances are included in deferred income on the balance sheets.