Reportable Segments (Segment Net Operating Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total Net Operating Income	$ 431,790	$ 326,063	$ 313,206
Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	158,045	131,564	112,984
Austin
Segment Reporting Information [Line Items]
Total Net Operating Income	93,311	60,474	58,648
Charlotte
Segment Reporting Information [Line Items]
Total Net Operating Income	77,082	62,812	62,708
Phoenix
Segment Reporting Information [Line Items]
Total Net Operating Income	37,247	36,875	34,074
Tampa
Segment Reporting Information [Line Items]
Total Net Operating Income	33,586	30,514	29,426
Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	7,473
Orlando
Segment Reporting Information [Line Items]
Total Net Operating Income			13,029
Other
Segment Reporting Information [Line Items]
Total Net Operating Income	25,046	3,824	2,337
Office
Segment Reporting Information [Line Items]
Total Net Operating Income	428,731	323,820	309,223
Office | Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	158,093	131,564	109,706
Office | Austin
Segment Reporting Information [Line Items]
Total Net Operating Income	93,311	60,474	58,648
Office | Charlotte
Segment Reporting Information [Line Items]
Total Net Operating Income	77,082	62,812	62,708
Office | Phoenix
Segment Reporting Information [Line Items]
Total Net Operating Income	37,247	36,875	34,074
Office | Tampa
Segment Reporting Information [Line Items]
Total Net Operating Income	33,586	30,514	29,426
Office | Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	7,473
Office | Orlando
Segment Reporting Information [Line Items]
Total Net Operating Income			13,029
Office | Other
Segment Reporting Information [Line Items]
Total Net Operating Income	21,939	1,581	1,632
Mixed-Use
Segment Reporting Information [Line Items]
Total Net Operating Income	3,059	2,243	3,983
Mixed-Use | Atlanta
Segment Reporting Information [Line Items]
Total Net Operating Income	(48)	0	3,278
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 | 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 | Dallas
Segment Reporting Information [Line Items]
Total Net Operating Income	0
Mixed-Use | Orlando
Segment Reporting Information [Line Items]
Total Net Operating Income			0
Mixed-Use | Other
Segment Reporting Information [Line Items]
Total Net Operating Income	$ 3,107	$ 2,243	$ 705