Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash Flows from Operating Activities:
Net Income	$ 350,715	$ 276,831	$ 181,222
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	167,101	162,535	145,940
Amortization of debt deferred costs and intangibles, net	2,790	2,562	2,650
Impairment loss	15,257	98	153
Equity in earnings of real estate joint ventures and partnerships, net	(27,074)	(20,642)	(19,300)
Gain on sale and acquisition of real estate joint venture and partnership interests	0	(48,322)	(879)
Gain on sale of property	(218,611)	(100,714)	(59,621)
Distributions of income from real estate joint ventures and partnerships	1,321	1,149	1,216
Changes in accrued rent and accounts receivable, net	(18,964)	(14,488)	(8,884)
Changes in unamortized lease costs and other assets, net	(13,299)	(16,900)	(14,617)
Changes in accounts payable, accrued expenses and other liabilities, net	4,970	8,963	5,971
Other, net	5,552	1,339	11,584
Net cash provided by operating activities	269,758	252,411	245,435
Cash Flows from Investing Activities:
Acquisition of real estate and land	(1,902)	(500,421)	(221,779)
Development and capital improvements	(133,336)	(101,179)	(83,702)
Proceeds from sale of property and real estate equity investments	433,661	234,952	101,516
Real estate joint ventures and partnerships - Investments	(37,173)	(52,834)	(30,053)
Real estate joint ventures and partnerships - Distributions of capital	28,791	51,714	35,341
Purchase of investments	(5,730)	(4,740)	0
Proceeds from investments	8,502	1,250	1,250
Other, net	6,179	5,086	295
Net cash provided by (used in) investing activities	298,992	(366,172)	(197,132)
Cash Flows from Financing Activities:
Proceeds from issuance of debt	0	249,999	448,083
Principal payments of debt	(28,723)	(144,788)	(240,505)
Changes in unsecured credit facilities	(245,000)	95,500	(39,500)
Proceeds from issuance of common shares of beneficial interest, net	1,588	137,460	42,572
Redemption of preferred shares of beneficial interest	0	0	(150,000)
Common and preferred dividends paid	(294,073)	(185,100)	(174,628)
Debt issuance and extinguishment costs paid	(488)	(5,396)	(9,878)
Distributions to noncontrolling interests	(19,342)	(9,563)	(5,478)
Contributions from noncontrolling interests	0	0	1,318
Other, net	(2,657)	(8,314)	1,768
Net cash (used in) provided by financing activities	(588,695)	129,798	(126,248)
Net (decrease) increase in cash, cash equivalents and restricted cash equivalents	(19,945)	16,037	(77,945)
Cash, cash equivalents and restricted cash equivalents at January 1	41,279	25,242	103,187
Cash, cash equivalents and restricted cash equivalents at December 31	21,334	41,279	25,242
Interest paid during the period (net of amount capitalized of $4,868, $2,656 and $3,252, respectively)	79,161	79,515	79,580
Income taxes paid during the period	$ 1,009	$ 958	$ 1,474