Segment Information (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	$ 117,057	$ 113,765	$ 232,036	$ 228,268
Total Net Operating Income	75,914	75,622	149,695	148,621
Depreciation and amortization	(33,430)	(33,260)	(67,147)	(65,898)
General and administrative expense	(7,978)	(6,980)	(15,771)	(15,487)
Interest expense	(23,907)	(22,934)	(47,450)	(46,047)
Interest and other income	1,875	965	3,748	2,665
Income from continuing operations before disposition of property, condominiums and investment in unconsolidated affiliates and equity in earnings of unconsolidated affiliates	12,474	13,413	23,075	23,854
Office Atlanta, GA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	12,341	12,065	24,245	24,198
Total Net Operating Income	7,973	7,828	15,467	15,461
Office Greenville, SC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	3,437	3,451	6,943	7,127
Total Net Operating Income	2,067	2,168	4,143	4,449
Office Kansas City, MO [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	3,586	3,663	7,243	7,371
Total Net Operating Income	2,113	2,327	4,228	4,540
Office Memphis, TN [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	10,077	7,328	20,180	15,196
Total Net Operating Income	5,462	4,223	11,224	9,507
Office Nashville, TN [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	15,362	14,851	29,977	29,964
Total Net Operating Income	10,329	10,065	19,981	19,934
Office Orlando, FL [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	2,619	3,059	4,937	6,064
Total Net Operating Income	1,285	1,723	2,451	3,336
Office Piedmont Triad, NC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	5,273	5,367	10,637	10,764
Total Net Operating Income	3,452	3,791	7,055	7,091
Office Raleigh, NC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	20,103	18,523	39,423	37,328
Total Net Operating Income	14,270	13,046	27,473	25,675
Office Richmond, VA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	11,668	11,483	23,047	23,276
Total Net Operating Income	8,232	8,405	16,092	16,355
Office Tampa, FL [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	17,458	18,037	34,250	35,979
Total Net Operating Income	10,802	10,991	21,192	21,811
Office Total Segment [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	101,924	97,827	200,882	197,267
Total Net Operating Income	65,985	64,567	129,306	128,159
Industrial Atlanta, GA [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	4,028	3,842	7,962	7,817
Total Net Operating Income	3,001	2,793	5,841	5,563
Industrial Piedmont Triad, NC [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	2,825	3,044	5,803	6,065
Total Net Operating Income	2,107	2,328	4,332	4,375
Industrial Total Segment [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	6,853	6,886	13,765	13,882
Total Net Operating Income	5,108	5,121	10,173	9,938
Retail Kansas City, MO [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	8,203	8,749	17,104	16,437
Total Net Operating Income	4,832	5,746	10,123	10,098
Total Retail Segment [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	8,203	8,749	17,104	16,437
Total Net Operating Income	4,832	5,746	10,123	10,098
Residential Kansas City, MO [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	77	303	285	682
Total Net Operating Income	(11)	188	93	426
Total Residential Segment [Member]
Segment Reporting Information [Line Items]
Total Rental and Other Revenues	77	303	285	682
Total Net Operating Income	$ (11)	$ 188	$ 93	$ 426