Reportable Segments - (Net Operating Income) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Net Operating Income	$ 117,132	$ 97,417	$ 244,914	$ 185,148
Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	41,696	39,368	86,491	76,766
Austin
Segment Reporting Information [Line Items]
Net Operating Income	31,229	18,577	60,523	34,525
Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	14,480	18,050	36,593	33,859
Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,580	669	7,219	670
Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	8,922	9,290	18,715	18,781
Tampa
Segment Reporting Information [Line Items]
Net Operating Income	7,998	8,573	16,142	16,560
Other
Segment Reporting Information [Line Items]
Net Operating Income	9,227	2,890	19,231	3,987
Office
Segment Reporting Information [Line Items]
Net Operating Income	116,315	96,709	243,281	183,572
Office | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	41,709	39,368	86,564	76,766
Office | Austin
Segment Reporting Information [Line Items]
Net Operating Income	31,229	18,577	60,523	34,525
Office | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	14,480	18,050	36,593	33,859
Office | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,580	669	7,219	670
Office | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	8,922	9,290	18,715	18,781
Office | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	7,998	8,573	16,142	16,560
Office | Other
Segment Reporting Information [Line Items]
Net Operating Income	8,397	2,182	17,525	2,411
Mixed-Use
Segment Reporting Information [Line Items]
Net Operating Income	817	708	1,633	1,576
Mixed-Use | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	(13)	0	(73)	0
Mixed-Use | Austin
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Mixed-Use | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Mixed-Use | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Mixed-Use | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Mixed-Use | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Mixed-Use | Other
Segment Reporting Information [Line Items]
Net Operating Income	$ 830	$ 708	$ 1,706	$ 1,576