Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	$ 203,841	$ 185,502	$ 410,219	$ 369,307
Total Net Operating Income	141,472	129,276	286,428	256,892
Reconciliation to net income:
Depreciation and amortization	(69,742)	(61,949)	(139,409)	(122,876)
Impairments of real estate assets	(35,000)	0	(35,000)	0
General and administrative expenses	(9,591)	(10,107)	(23,147)	(20,059)
Interest expense	(25,027)	(19,001)	(49,420)	(38,769)
Other income	120	332	483	644
Gains on disposition of property	50,044	22,862	54,144	41,799
Equity in earnings of unconsolidated affiliates	326	431	626	1,068
Net income	52,602	61,844	94,705	118,699
Total Office Segment [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	202,710	182,204	407,765	362,577
Total Net Operating Income	140,802	127,209	284,939	252,884
Office Atlanta, GA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	35,447	35,738	71,001	71,713
Total Net Operating Income	23,267	23,622	46,948	47,622
Office Charlotte, NC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	16,874	8,917	33,818	18,051
Total Net Operating Income	12,807	7,035	25,857	14,287
Office Nashville, TN [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	42,606	35,578	86,053	70,737
Total Net Operating Income	31,417	25,824	63,939	50,817
Office Orlando, FL [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	13,352	12,730	26,664	25,289
Total Net Operating Income	8,262	7,782	16,399	15,494
Office Pittsburgh, PA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	14,908	13,949	29,854	28,567
Total Net Operating Income	9,051	8,411	17,912	17,300
Office Raleigh, NC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	45,535	37,655	91,831	74,697
Total Net Operating Income	34,020	28,444	68,735	56,580
Office Richmond, VA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	10,432	11,751	20,965	23,213
Total Net Operating Income	7,363	8,234	14,588	16,287
Office Tampa, FL [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	23,556	25,886	47,579	50,310
Total Net Operating Income	14,615	17,857	30,561	34,497
Other [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	1,131	3,298	2,454	6,730
Total Net Operating Income	$ 670	$ 2,067	$ 1,489	$ 4,008