Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Document Period End Date	Sep. 30, 2016
PROPERTIES:
Operating properties, net of accumulated depreciation of $377,418 and $352,350 in 2016 and 2015, respectively	$ 2,014,548	$ 2,194,781
Projects under development	111,768	27,890
Land	9,669	17,829
Total properties	2,135,985	2,240,500
Real Estate Held-for-sale	203,735	7,246
Cash and cash equivalents	97,241	2,003
Restricted cash	6,566	4,304
Notes and accounts receivable, net of allowance for doubtful accounts of $1,100 and $1,353 in 2016 and 2015, respectively	12,215	10,828
Deferred rents receivable	60,094	67,258
Investment in unconsolidated joint ventures	116,933	102,577
Intangible assets, net of accumulated amortization of $109,328 and $103,458 in 2016 and 2015, respectively	105,015	124,615
Other assets	22,950	35,989
Total assets	2,760,734	2,595,320
LIABILITIES AND EQUITY
Notes payable	789,378	718,810
Accounts payable and accrued expenses	84,641	71,739
Deferred income	34,604	29,788
Intangible liabilities, net of accumulated amortization of $29,199 and $26,890 in 2016 and 2015, respectively	52,127	59,592
Other liabilities	28,412	30,629
Disposal Group, Including Discontinued Operation, Liabilities, Current	106,135	1,347
Total liabilities	1,095,297	911,905
STOCKHOLDERS' INVESTMENT:
Common stock, $1 par value, 350,000,000 shares authorized, 220,436,378 and 220,255,676 shares issued in 2016 and 2015, respectively	220,499	220,256
Additional paid-in capital	1,723,552	1,722,224
Treasury stock at cost, 10,329,082 and 8,742,181 shares in 2016 and 2015, respectively	(148,373)	(134,630)
Distributions in excess of cumulative net income	(132,766)	(124,435)
Nonredeemable Noncontrolling Interest	2,525	0
Total equity	1,665,437	1,683,415
Total liabilities and equity	$ 2,760,734	$ 2,595,320