Investment in Unconsolidated Joint Ventures (Summary of Financial Data and Principal Activities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
SUMMARY OF FINANCIAL POSITION:
Total Assets	$ 784,970		$ 930,904
Total Debt	434,553		526,458
Total Equity	314,794		366,113
Company’s Investment	78,908		156,388
SUMMARY OF OPERATIONS:
Total Revenues	57,513	$ 53,080
Net Income (Loss)	68,713	11,638
Company's Share of Income (Loss)	40,901	3,618
Terminus Office Holdings
SUMMARY OF FINANCIAL POSITION:
Total Assets	267,747		268,242
Total Debt	205,454		207,545
Total Equity	51,112		49,476
Company’s Investment	25,384		25,686
SUMMARY OF OPERATIONS:
Total Revenues	21,908	20,978
Net Income (Loss)	3,178	2,597
Company's Share of Income (Loss)	1,769	1,298
EP I LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	1,760		78,537
Total Debt	0		58,029
Total Equity	1,333		18,962
Company’s Investment	783		18,551
SUMMARY OF OPERATIONS:
Total Revenues	4,103	5,991
Net Income (Loss)	44,929	1,168
Company's Share of Income (Loss)	28,525	951
EP II LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	520		67,754
Total Debt	0		44,969
Total Equity	239		21,743
Company’s Investment	88		17,606
SUMMARY OF OPERATIONS:
Total Revenues	2,643	2,044
Net Income (Loss)	12,967	(1,018)
Company's Share of Income (Loss)	9,725	(823)
Charlotte Gateway Village, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	125,819		119,054
Total Debt	0		0
Total Equity	121,544		116,809
Company’s Investment	14,163		11,796
SUMMARY OF OPERATIONS:
Total Revenues	13,380	17,477
Net Income (Loss)	4,734	7,263
Company's Share of Income (Loss)	2,367	987
HICO Victory Center LP
SUMMARY OF FINANCIAL POSITION:
Total Assets	14,145		14,124
Total Debt	0		0
Total Equity	14,141		13,869
Company’s Investment	9,632		9,506
SUMMARY OF OPERATIONS:
Total Revenues	171	169
Net Income (Loss)	171	162
Company's Share of Income (Loss)	114	81
Carolina Square Holdings LP
SUMMARY OF FINANCIAL POSITION:
Total Assets	88,571		66,922
Total Debt	50,529		23,741
Total Equity	34,087		34,173
Company’s Investment	18,752		18,325
SUMMARY OF OPERATIONS:
Total Revenues	40	0
Net Income (Loss)	(94)	0
Company's Share of Income (Loss)	0	0
CL Realty, L.L.C.
SUMMARY OF FINANCIAL POSITION:
Total Assets	7,989		8,047
Total Debt	0		0
Total Equity	7,915		7,899
Company’s Investment	2,874		3,644
SUMMARY OF OPERATIONS:
Total Revenues	2,599	246
Net Income (Loss)	2,415	64
Company's Share of Income (Loss)	430	44
DC Charlotte Plaza LLLP
SUMMARY OF FINANCIAL POSITION:
Total Assets	30,780		17,940
Total Debt	0		0
Total Equity	24,209		17,073
Company’s Investment	12,528		8,937
SUMMARY OF OPERATIONS:
Total Revenues	2	0
Net Income (Loss)	2	33
Company's Share of Income (Loss)	2	18
Temco Associates, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	4,398		4,368
Total Debt	0		0
Total Equity	4,294		4,253
Company’s Investment	854		829
SUMMARY OF OPERATIONS:
Total Revenues	80	147
Net Income (Loss)	41	79
Company's Share of Income (Loss)	25	119
Wildwood Associates
SUMMARY OF FINANCIAL POSITION:
Total Assets	16,380		16,351
Total Debt	0		0
Total Equity	16,262		16,314
Company’s Investment	(1,169)		(1,143)
SUMMARY OF OPERATIONS:
Total Revenues	0	0
Net Income (Loss)	(51)	(56)
Company's Share of Income (Loss)	(26)	(28)
Crawford Long - CPI, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	28,400		27,523
Total Debt	72,070		72,822
Total Equity	(45,106)		(45,928)
Company’s Investment	(21,455)		(21,866)
SUMMARY OF OPERATIONS:
Total Revenues	6,033	6,028
Net Income (Loss)	1,516	1,346
Company's Share of Income (Loss)	758	673
111 West Rio Building
SUMMARY OF FINANCIAL POSITION:
Total Assets	0		59,399
Total Debt	0		12,852
Total Equity	0		32,855
Company’s Investment	0		52,206
SUMMARY OF OPERATIONS:
Total Revenues	0	0
Net Income (Loss)	0	0
Company's Share of Income (Loss)	(2,593)	0
Courvoisier Centre JV, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	181,633		172,197
Total Debt	106,500		106,500
Total Equity	68,400		69,479
Company’s Investment	11,588		11,782
SUMMARY OF OPERATIONS:
Total Revenues	6,554	0
Net Income (Loss)	(1,083)	0
Company's Share of Income (Loss)	(195)	0
HICO Avalon II, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	5,237		0
Total Debt	0		0
Total Equity	5,237		0
Company’s Investment	3,928		0
SUMMARY OF OPERATIONS:
Total Revenues	0	0
Net Income (Loss)	0	0
Company's Share of Income (Loss)	0	0
AMCO 120 WT Holdings, LLC
SUMMARY OF FINANCIAL POSITION:
Total Assets	11,591		10,446
Total Debt	0		0
Total Equity	11,127		9,136
Company’s Investment	617		184
SUMMARY OF OPERATIONS:
Total Revenues	0	0
Net Income (Loss)	(12)	0
Company's Share of Income (Loss)	0	0
Other
SUMMARY OF FINANCIAL POSITION:
Total Assets	0		0
Total Debt	0		0
Total Equity	0		0
Company’s Investment	341		$ 345
SUMMARY OF OPERATIONS:
Total Revenues	0	0
Net Income (Loss)	0	0
Company's Share of Income (Loss)	$ 0	$ 298