Segment Reporting - NOI by Geographical Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	$ 78,782	$ 81,416	$ 156,441	$ 165,218
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	76,375	78,183	152,736	155,202
Corporate and other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	2,407	3,233	3,705	10,016
Dallas | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	17,244	15,899	34,020	28,389
Atlanta | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	14,703	15,023	29,598	29,934
Washington, D.C. | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	9,188	9,306	17,659	19,435
Minneapolis | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	8,414	8,066	16,467	16,766
Boston | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	11,048	10,552	21,771	21,249
Orlando | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	7,839	7,995	18,088	16,972
New York | Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net operating income	$ 7,939	$ 11,342	$ 15,133	$ 22,457