Reportable Segments - Segment Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Total Revenues	$ 188,732	$ 183,380	$ 564,919	$ 557,193
Rental property revenues
Segment Reporting Information [Line Items]
Total Revenues	185,515	179,024	552,088	543,252
Rental property revenues | Office
Segment Reporting Information [Line Items]
Total Revenues	184,794	178,220	550,215	541,897
Rental property revenues | Other
Segment Reporting Information [Line Items]
Total Revenues	721	804	1,873	1,355
Rental property revenues | Operating segments
Segment Reporting Information [Line Items]
Total Revenues	193,509	185,246	575,462	565,188
Rental property revenues | Operating segments | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	68,328	64,852	199,500	193,351
Rental property revenues | Operating segments | Austin
Segment Reporting Information [Line Items]
Total Revenues	65,448	52,008	183,158	155,009
Rental property revenues | Operating segments | Charlotte
Segment Reporting Information [Line Items]
Total Revenues	18,248	20,370	62,451	75,411
Rental property revenues | Operating segments | Dallas
Segment Reporting Information [Line Items]
Total Revenues	4,337	4,601	13,351	13,559
Rental property revenues | Operating segments | Phoenix
Segment Reporting Information [Line Items]
Total Revenues	12,847	12,689	38,067	37,932
Rental property revenues | Operating segments | Tampa
Segment Reporting Information [Line Items]
Total Revenues	14,444	13,179	43,180	40,203
Rental property revenues | Operating segments | Other
Segment Reporting Information [Line Items]
Total Revenues	9,857	17,547	35,755	49,723
Rental property revenues | Operating segments | Office
Segment Reporting Information [Line Items]
Total Revenues	191,264	183,140	568,620	559,969
Rental property revenues | Operating segments | Office | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	67,959	64,742	198,461	193,117
Rental property revenues | Operating segments | Office | Austin
Segment Reporting Information [Line Items]
Total Revenues	65,448	52,008	183,158	155,009
Rental property revenues | Operating segments | Office | Charlotte
Segment Reporting Information [Line Items]
Total Revenues	17,527	19,567	60,578	74,057
Rental property revenues | Operating segments | Office | Dallas
Segment Reporting Information [Line Items]
Total Revenues	4,337	4,601	13,351	13,559
Rental property revenues | Operating segments | Office | Phoenix
Segment Reporting Information [Line Items]
Total Revenues	12,847	12,689	38,067	37,932
Rental property revenues | Operating segments | Office | Tampa
Segment Reporting Information [Line Items]
Total Revenues	14,444	13,179	43,180	40,203
Rental property revenues | Operating segments | Office | Other
Segment Reporting Information [Line Items]
Total Revenues	8,702	16,354	31,825	46,092
Rental property revenues | Operating segments | Other
Segment Reporting Information [Line Items]
Total Revenues	2,245	2,106	6,842	5,219
Rental property revenues | Operating segments | Other | Atlanta
Segment Reporting Information [Line Items]
Total Revenues	369	110	1,039	234
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	721	803	1,873	1,354
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	1,155	1,193	3,930	3,631
Rental property revenues | Segment reconciling items
Segment Reporting Information [Line Items]
Total Revenues	(7,994)	(6,222)	(23,374)	(21,936)
Rental property revenues | Segment reconciling items | Office
Segment Reporting Information [Line Items]
Total Revenues	(6,470)	(4,920)	(18,405)	(18,072)
Rental property revenues | Segment reconciling items | Other
Segment Reporting Information [Line Items]
Total Revenues	$ (1,524)	$ (1,302)	$ (4,969)	$ (3,864)