Reportable Segments - Net Operating Income (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]
Net Operating Income	$ 124,148	$ 120,016	$ 369,977	$ 364,930
Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	44,513	43,388	130,984	129,879
Austin
Segment Reporting Information [Line Items]
Net Operating Income	38,532	31,639	108,764	92,161
Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	12,852	14,621	43,972	51,214
Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,424	3,688	10,546	10,907
Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	9,299	9,205	27,252	27,920
Tampa
Segment Reporting Information [Line Items]
Net Operating Income	9,434	8,230	27,755	24,372
Other
Segment Reporting Information [Line Items]
Net Operating Income	6,094	9,245	20,704	28,477
Office
Segment Reporting Information [Line Items]
Net Operating Income	122,860	118,730	366,186	361,662
Office | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	44,333	43,399	130,551	129,992
Office | Austin
Segment Reporting Information [Line Items]
Net Operating Income	38,532	31,639	108,764	92,161
Office | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	12,491	14,086	43,176	50,302
Office | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,424	3,688	10,546	10,907
Office | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	9,299	9,205	27,252	27,920
Office | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	9,434	8,230	27,755	24,372
Office | Other
Segment Reporting Information [Line Items]
Net Operating Income	5,347	8,483	18,142	26,008
Other
Segment Reporting Information [Line Items]
Net Operating Income	1,288	1,286	3,791	3,268
Other | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	180	(11)	433	(113)
Other | Austin
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Other | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	361	535	796	912
Other | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Other | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Other | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Other | Other
Segment Reporting Information [Line Items]
Net Operating Income	$ 747	$ 762	$ 2,562	$ 2,469