Investment in Unconsolidated Joint Ventures (Summary of Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
SUMMARY OF FINANCIAL POSITION
Total Assets	$ 643,134	$ 930,904
Total Debt	338,590	526,458
Total Equity (Deficit)	267,423	366,113
Company's Investment	78,940	156,388
Terminus Office Holdings
SUMMARY OF FINANCIAL POSITION
Total Assets	261,999	268,242
Total Debt	203,131	207,545
Total Equity (Deficit)	48,033	49,476
Company's Investment	24,898	25,686
DC Charlotte Plaza LLLP
SUMMARY OF FINANCIAL POSITION
Total Assets	53,791	17,940
Total Debt	0	0
Total Equity (Deficit)	42,853	17,073
Company's Investment	22,293	8,937
Carolina Square Holdings LP
SUMMARY OF FINANCIAL POSITION
Total Assets	106,580	66,922
Total Debt	64,412	23,741
Total Equity (Deficit)	33,648	34,173
Company's Investment	19,384	18,325
Charlotte Gateway Village, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	124,691	119,054
Total Debt	0	0
Total Equity (Deficit)	121,386	116,809
Company's Investment	14,568	11,796
HICO Victory Center LP
SUMMARY OF FINANCIAL POSITION
Total Assets	14,403	14,124
Total Debt	0	0
Total Equity (Deficit)	14,401	13,869
Company's Investment	9,752	9,506
HICO Avalon II, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	6,379	0
Total Debt	0	0
Total Equity (Deficit)	6,303	0
Company's Investment	4,931	0
CL Realty, L.L.C.
SUMMARY OF FINANCIAL POSITION
Total Assets	8,287	8,047
Total Debt	0	0
Total Equity (Deficit)	8,127	7,899
Company's Investment	2,980	3,644
AMCO 120 WT Holdings, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	18,066	10,446
Total Debt	0	0
Total Equity (Deficit)	16,354	9,136
Company's Investment	1,664	184
Temco Associates, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	4,441	4,368
Total Debt	0	0
Total Equity (Deficit)	4,337	4,253
Company's Investment	875	829
EP II LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	277	67,754
Total Debt	0	44,969
Total Equity (Deficit)	180	21,743
Company's Investment	44	17,606
EP I LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	521	78,537
Total Debt	0	58,029
Total Equity (Deficit)	319	18,962
Company's Investment	25	18,551
Courvoisier Centre JV, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	0	172,197
Total Debt	0	106,500
Total Equity (Deficit)	0	69,479
Company's Investment	0	11,782
111 West Rio Building
SUMMARY OF FINANCIAL POSITION
Total Assets	0	59,399
Total Debt	0	12,852
Total Equity (Deficit)	0	32,855
Company's Investment	0	52,206
Wildwood Associates
SUMMARY OF FINANCIAL POSITION
Total Assets	16,337	16,351
Total Debt	0	0
Total Equity (Deficit)	16,297	16,314
Company's Investment	(1,151)	(1,143)
Crawford Long - CPI, LLC
SUMMARY OF FINANCIAL POSITION
Total Assets	27,362	27,523
Total Debt	71,047	72,822
Total Equity (Deficit)	(44,815)	(45,928)
Company's Investment	(21,323)	(21,866)
Other
SUMMARY OF FINANCIAL POSITION
Total Assets	0	0
Total Debt	0	0
Total Equity (Deficit)	0	0
Company's Investment	$ 0	$ 345