Reportable Segments (Net Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Net Operating Income	$ 127,782	$ 87,731
Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	44,795	37,399
Austin
Segment Reporting Information [Line Items]
Net Operating Income	29,294	15,948
Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	22,113	15,808
Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,639
Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	9,793	9,491
Tampa
Segment Reporting Information [Line Items]
Net Operating Income	8,144	7,988
Other
Segment Reporting Information [Line Items]
Net Operating Income	10,004	1,097
Office
Segment Reporting Information [Line Items]
Net Operating Income	126,966	86,864
Office | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	44,855	37,399
Office | Austin
Segment Reporting Information [Line Items]
Net Operating Income	29,294	15,948
Office | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	22,113	15,808
Office | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,639
Office | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	9,793	9,491
Office | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	8,144	7,988
Office | Other
Segment Reporting Information [Line Items]
Net Operating Income	9,128	230
Mixed-Use
Segment Reporting Information [Line Items]
Net Operating Income	816	867
Mixed-Use | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	(60)	0
Mixed-Use | Austin
Segment Reporting Information [Line Items]
Net Operating Income	0	0
Mixed-Use | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	0	0
Mixed-Use | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	0
Mixed-Use | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	0	0
Mixed-Use | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	0	0
Mixed-Use | Other
Segment Reporting Information [Line Items]
Net Operating Income	$ 876	$ 867