Quarterly Financial Data (Schedule Of Quarterly Financial Information) (Details) (USD $)	3 Months Ended																12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Selected Quarterly Financial Information [Line Items]
Revenues	$ 126,102,000	[1]	$ 130,521,000	[1]	$ 130,191,000	[1]	$ 127,592,000	[1]	$ 126,071,000	[1]	$ 123,302,000	[1]	$ 121,995,000	[1]	$ 117,827,000	[1]	$ 514,406,000	$ 489,195,000	$ 451,177,000
Net income	103,615,000	[2],[3]	102,199,000	[2],[4]	36,984,000	[2],[5]	64,781,000	[2],[6]	53,772,000	[2]	62,389,000	[2]	104,178,000	[2]	44,817,000	[2],[7]	307,579,000	265,156,000	152,421,000
Net income attributable to common shareholders	86,270,000	[2],[3],[8]	97,619,000	[2],[4]	32,686,000	[2],[5]	60,593,000	[2],[6]	47,224,000	[2]	57,832,000	[2]	45,421,000	[2],[9]	33,668,000	[2],[7]	277,168,000	184,145,000	109,210,000
Earnings per common share - basic	$ 0.71	[2],[3],[8]	$ 0.80	[2],[4]	$ 0.27	[2],[5]	$ 0.50	[2],[6]	$ 0.39	[2]	$ 0.48	[2]	$ 0.37	[2],[9]	$ 0.28	[2],[7]	$ 2.28	$ 1.52	$ 0.90
Earnings per common share - diluted	$ 0.70	[2],[3],[8]	$ 0.79	[2],[4]	$ 0.27	[2],[5]	$ 0.49	[2],[6]	$ 0.38	[2]	$ 0.47	[2]	$ 0.37	[2],[9]	$ 0.28	[2],[7]	$ 2.25	$ 1.50	$ 0.90
Gain on sale of properties and real estate joint venture and partnership interests and on acquisitions	74,900,000		69,500,000		6,800,000		41,400,000		25,200,000		38,400,000		78,400,000		11,700,000
Accelerated depreciation							3,600,000										150,356,000	146,763,000	127,703,000
Recovery of receivable							1,500,000
Tax benefit					2,100,000												1,261,000	(7,046,000)	75,000
Gain on sale of property																	167,600,000
Write-off of debt costs			1,200,000														1,200,000
Impairment loss	1,000,000																1,024,000	2,579,000	9,585,000
Net income attributable to noncontrolling interests	14,600,000												37,700,000				19,571,000	44,894,000	5,781,000
Redemption costs of preferred shares																	0	17,944,000	2,500,000
6.5% Series F Preferred Shares [Member]
Schedule of Selected Quarterly Financial Information [Line Items]
Redemption costs of preferred shares													15,700,000					15,700,000
Acceleration Of Mortgage Intangible Amortization [Member]
Schedule of Selected Quarterly Financial Information [Line Items]
Amortization (accretion)															(9,700,000)			(9,700,000)
Unconsolidated [Member]
Schedule of Selected Quarterly Financial Information [Line Items]
Gain on sale of property	$ 1,900,000		$ 2,900,000														$ 4,900,000	$ 16,000,000
8.1% Senior Unsecured Notes [Member]
Schedule of Selected Quarterly Financial Information [Line Items]
Debt stated interest rate	8.10%		8.10%														8.10%

[1] Revenues from the sale of operating properties classified as discontinued operations have been reclassified and reported in discontinued operations for all periods presented.

[2] The quarter results include significant gains on the sale of properties and real estate joint venture and partnership interests and on acquisitions. Gain amounts are: $41.4 million, $6.8 million, $69.5 million and $74.9 million for the three months ended March 31, 2014, June 30, 2014, September 30, 2014 and December 31, 2014, respectively, and $11.7 million, $78.4 million, $38.4 million and $25.2 million for the three months ended March 31, 2013, June 30, 2013, September 30, 2013 and December 31, 2013, respectively.

[3] The quarter results include gains on the sale of properties in our equity method investments of $1.9 million and a $1.0 million impairment loss associated primarily with the disposition of a land parcel and a shopping center.

[4] The quarter results include gains on the sale of properties in our equity method investments of $2.9 million and a $1.2 million write-off of debt costs associated with the redemption of our 8.1% senior unsecured notes.

[5] The quarter results include the realization of a $2.1 million tax benefit associated with the sale of unimproved land in our taxable REIT subsidiary.

[6] The quarter results include accelerated depreciation of $3.6 million related to a redevelopment project and a $1.5 million recovery of a receivable.

[7] The quarter results include a write-off of an above-market assumed mortgage intangible due to the early payoff of the related mortgage of $9.7 million.

[8] The quarter results include net income attributable to noncontrolling interests of $14.6 million associated with applicable gains discussed in (2) above.

[9] The quarter results include net income attributable to noncontrolling interests of $37.7 million associated with applicable gains discussed in (2) above and a $15.7 million deduction associated with the redemption of Series F preferred shares (see Note 9 for additional information).