Reportable Segments - Segment Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Total Revenues	$ 186,637	$ 179,915	$ 376,187	$ 373,813
Rental property revenues
Segment Reporting Information [Line Items]
Total Revenues	181,766	175,099	366,573	364,228
Rental property revenues | Office
Segment Reporting Information [Line Items]
Total Revenues	181,175	174,548	365,421	363,677
Rental property revenues | Other
Segment Reporting Information [Line Items]
Total Revenues	591	551	1,152	551
Rental property revenues | Operating segments
Segment Reporting Information [Line Items]
Total Revenues	189,908	181,248	381,953	379,943
Rental property revenues | Operating segments | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	66,022	62,586	131,172	128,499
Rental property revenues | Operating segments | Austin
Segment Reporting Information [Line Items]
Total Revenues	59,677	52,455	117,710	101,202
Rental property revenues | Operating segments | Charlotte
Segment Reporting Information [Line Items]
Total Revenues	22,475	20,505	44,203	55,041
Rental property revenues | Operating segments | Dallas
Segment Reporting Information [Line Items]
Total Revenues	4,531	4,487	9,014	8,958
Rental property revenues | Operating segments | Phoenix
Segment Reporting Information [Line Items]
Total Revenues	12,482	12,084	25,220	25,243
Rental property revenues | Operating segments | Tampa
Segment Reporting Information [Line Items]
Total Revenues	14,165	12,912	28,736	27,024
Rental property revenues | Operating segments | Other
Segment Reporting Information [Line Items]
Total Revenues	10,556	16,219	25,898	33,976
Rental property revenues | Operating segments | Office
Segment Reporting Information [Line Items]
Total Revenues	187,391	179,432	377,356	376,830
Rental property revenues | Operating segments | Office | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	65,626	62,497	130,502	128,375
Rental property revenues | Operating segments | Office | Austin
Segment Reporting Information [Line Items]
Total Revenues	59,677	52,455	117,710	101,202
Rental property revenues | Operating segments | Office | Charlotte
Segment Reporting Information [Line Items]
Total Revenues	21,884	19,954	43,051	54,490
Rental property revenues | Operating segments | Office | Dallas
Segment Reporting Information [Line Items]
Total Revenues	4,531	4,487	9,014	8,958
Rental property revenues | Operating segments | Office | Phoenix
Segment Reporting Information [Line Items]
Total Revenues	12,482	12,084	25,220	25,243
Rental property revenues | Operating segments | Office | Tampa
Segment Reporting Information [Line Items]
Total Revenues	14,165	12,912	28,736	27,024
Rental property revenues | Operating segments | Office | Other
Segment Reporting Information [Line Items]
Total Revenues	9,026	15,043	23,123	31,538
Rental property revenues | Operating segments | Other
Segment Reporting Information [Line Items]
Total Revenues	2,517	1,816	4,597	3,113
Rental property revenues | Operating segments | Other | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	396	89	670	124
Rental property revenues | Operating segments | Other | Austin
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Rental property revenues | Operating segments | Other | Charlotte
Segment Reporting Information [Line Items]
Total Revenues	591	551	1,152	551
Rental property revenues | Operating segments | Other | Dallas
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Rental property revenues | Operating segments | Other | Phoenix
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Rental property revenues | Operating segments | Other | Tampa
Segment Reporting Information [Line Items]
Total Revenues	0	0	0	0
Rental property revenues | Operating segments | Other | Other
Segment Reporting Information [Line Items]
Total Revenues	1,530	1,176	2,775	2,438
Rental property revenues | Segment reconciling items
Segment Reporting Information [Line Items]
Total Revenues	(8,142)	(6,149)	(15,380)	(15,715)
Rental property revenues | Segment reconciling items | Office
Segment Reporting Information [Line Items]
Total Revenues	(6,216)	(4,884)	(11,935)	(13,153)
Rental property revenues | Segment reconciling items | Other
Segment Reporting Information [Line Items]
Total Revenues	$ (1,926)	$ (1,265)	$ (3,445)	$ (2,562)