Reportable Segments - Net Operating Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information [Line Items]
Net Operating Income	$ 122,705	$ 117,132	$ 245,829	$ 244,914
Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	43,274	41,696	86,471	86,491
Austin
Segment Reporting Information [Line Items]
Net Operating Income	35,955	31,229	70,232	60,523
Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	15,863	14,480	31,120	36,593
Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,571	3,580	7,122	7,219
Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	8,928	8,922	17,953	18,715
Tampa
Segment Reporting Information [Line Items]
Net Operating Income	8,919	7,998	18,321	16,142
Other
Segment Reporting Information [Line Items]
Net Operating Income	6,195	9,227	14,610	19,231
Office
Segment Reporting Information [Line Items]
Net Operating Income	121,430	115,967	243,326	242,933
Office | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	43,115	41,738	86,218	86,593
Office | Austin
Segment Reporting Information [Line Items]
Net Operating Income	35,955	31,229	70,232	60,523
Office | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	15,688	14,103	30,685	36,216
Office | Dallas
Segment Reporting Information [Line Items]
Net Operating Income	3,571	3,580	7,122	7,219
Office | Phoenix
Segment Reporting Information [Line Items]
Net Operating Income	8,928	8,922	17,953	18,715
Office | Tampa
Segment Reporting Information [Line Items]
Net Operating Income	8,919	7,998	18,321	16,142
Office | Other
Segment Reporting Information [Line Items]
Net Operating Income	5,254	8,397	12,795	17,525
Other
Segment Reporting Information [Line Items]
Net Operating Income	1,275	1,165	2,503	1,981
Other | Atlanta
Segment Reporting Information [Line Items]
Net Operating Income	159	(42)	253	(102)
Other | Austin
Segment Reporting Information [Line Items]
Net Operating Income	0	0	0	0
Other | Charlotte
Segment Reporting Information [Line Items]
Net Operating Income	175	377	435	377
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	$ 941	$ 830	$ 1,815	$ 1,706