Reportable Segments - Segment Net Operating Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Total Net Operating Income	$ 486,034	$ 431,790	$ 326,063
Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	172,539	158,045	131,564
Austin
Segment Reporting Information [Line Items]
Total Net Operating Income	125,215	93,311	60,474
Charlotte
Segment Reporting Information [Line Items]
Total Net Operating Income	65,203	77,082	62,812
Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	14,586	7,473
Phoenix
Segment Reporting Information [Line Items]
Total Net Operating Income	37,358	37,247	36,875
Tampa
Segment Reporting Information [Line Items]
Total Net Operating Income	33,440	33,586	30,514
Other
Segment Reporting Information [Line Items]
Total Net Operating Income	37,693	25,046	3,824
Office
Segment Reporting Information [Line Items]
Total Net Operating Income	482,736	428,731	323,820
Office | Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	172,588	158,093	131,564
Office | Austin
Segment Reporting Information [Line Items]
Total Net Operating Income	125,215	93,311	60,474
Office | Charlotte
Segment Reporting Information [Line Items]
Total Net Operating Income	65,203	77,082	62,812
Office | Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	14,586	7,473
Office | Phoenix
Segment Reporting Information [Line Items]
Total Net Operating Income	37,358	37,247	36,875
Office | Tampa
Segment Reporting Information [Line Items]
Total Net Operating Income	33,440	33,586	30,514
Office | Other
Segment Reporting Information [Line Items]
Total Net Operating Income	34,346	21,939	1,581
Mixed-Use
Segment Reporting Information [Line Items]
Total Net Operating Income	3,298	3,059	2,243
Mixed-Use | Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	(49)	(48)	0
Mixed-Use | Austin
Segment Reporting Information [Line Items]
Total Net Operating Income	0	0	0
Mixed-Use | Charlotte
Segment Reporting Information [Line Items]
Total Net Operating Income	0	0	0
Mixed-Use | Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	0	0
Mixed-Use | Phoenix
Segment Reporting Information [Line Items]
Total Net Operating Income	0	0	0
Mixed-Use | Tampa
Segment Reporting Information [Line Items]
Total Net Operating Income	0	0	0
Mixed-Use | Other
Segment Reporting Information [Line Items]
Total Net Operating Income	$ 3,347	$ 3,107	$ 2,243