Investment in Unconsolidated Joint Ventures - Summary of Financial Position (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
SUMMARY OF FINANCIAL POSITION
Total Assets	$ 7,107,398		$ 7,151,447
Total Debt	230,300
Total Equity (Deficit)	4,467,134		4,359,274
Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	590,853		658,303
Total Debt	230,305		165,039
Total Equity (Deficit)	244,186		354,404
Company's Investment	107,192		114,158
DC Charlotte Plaza LLLP | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	173,704		179,694
Total Debt	0		0
Total Equity (Deficit)	90,648		90,373
Company's Investment	47,941		48,058
Austin 300 Colorado Project, LP
SUMMARY OF FINANCIAL POSITION
Total Debt	86,800
Austin 300 Colorado Project, LP | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	165,586		112,630
Total Debt	86,848		21,430
Total Equity (Deficit)	68,567		68,101
Company's Investment	38,488		36,846
AMCO 120 WT Holdings, LLC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	85,449		77,377
Total Debt	0		0
Total Equity (Deficit)	84,311		70,696
Company's Investment	15,735		13,362
Carolina Square Holdings LP | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	118,616		114,483
Total Debt	77,034		75,662
Total Equity (Deficit)	21,888		25,184
Company's Investment	12,430		14,414
HICO Victory Center LP | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	16,544		16,045
Total Debt	0		0
Total Equity (Deficit)	15,709		15,353
Company's Investment	10,595		10,373
Charlotte Gateway Village, LLC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	0		109,675
Total Debt	0		0
Total Equity (Deficit)	0		106,651
Company's Investment	0		6,718
Wildwood Associates
SUMMARY OF FINANCIAL POSITION
Company's Investment		$ 520,000
Wildwood Associates | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	0		11,061
Total Debt	0		0
Total Equity (Deficit)	0		10,978
Company's Investment	0		(521)
Crawford Long - CPI, LLC
SUMMARY OF FINANCIAL POSITION
Total Debt	66,400
Crawford Long - CPI, LLC | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	29,641		28,459
Total Debt	66,423		67,947
Total Equity (Deficit)	(38,253)		(40,250)
Company's Investment	(18,289)		(19,205)
Other | Equity Method Investment, Nonconsolidated Investee or Group of Investees
SUMMARY OF FINANCIAL POSITION
Total Assets	1,313		8,879
Total Debt	0		0
Total Equity (Deficit)	1,316		7,318
Company's Investment	$ 292		$ 4,113