Consolidated Statements of Cash Flows In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Cash flow from operating activities:
Net income	$ 280,275	$ 182,090	$ 161,651
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	262,742	251,139	247,637
Loss on operating/development properties held for sale/sold/transferred			57
Impairment charges	59,569	32,763	39,121
Gain on sale of development properties		(12,074)	(2,130)
Gain on sale of operating properties	(94,369)	(17,435)	(4,366)
Equity in income of joint ventures, net	(112,896)	(63,467)	(55,705)
Gains on change in control of interests	(15,555)	(569)
Equity in income from other real estate investments, net	(53,397)	(51,813)	(39,642)
Distributions from joint ventures and other real estate investments	194,110	163,048	162,860
Cash retained from excess tax benefits			(103)
Change in accounts and notes receivable	2,940	(19,271)	(17,388)
Change in accounts payable and accrued expenses	(11,281)	(8,082)	15,811
Change in other operating assets and liabilities	(33,084)	(7,716)	(27,868)
Net cash flow provided by operating activities	479,054	448,613	479,935
Cash flow from investing activities:
Acquisition of and improvements to operating real estate	(552,469)	(343,299)	(182,482)
Acquisition of and improvements to real estate under development	(2,487)	(37,896)	(41,975)
Investment in marketable securities			(9,041)
Proceeds from sale/repayments of marketable securities	156	188,003	30,455
Investments and advances to real estate joint ventures	(219,885)	(171,695)	(138,796)
Reimbursements of investments and advances to real estate joint ventures	187,856	63,529	85,205
Other real estate investments	(5,638)	(6,958)	(12,528)
Reimbursements of investments and advances to other real estate investments	33,720	68,881	30,861
Investment in mortgage loans receivable	(16,021)		(2,745)
Collection of mortgage loans receivable	63,600	19,148	27,587
Other investments	(924)	(730)	(4,004)
Reimbursements of other investments	11,553	20,116	8,792
Proceeds from sale of operating properties	449,539	135,646	238,746
Proceeds from sale of development properties		44,495	7,829
Net cash flow (used for)/provided by investing activities	(51,000)	(20,760)	37,904
Cash flow from financing activities:
Principal payments on debt, excluding normal amortization of rental property debt	(284,815)	(62,470)	(226,155)
Principal payments on rental property debt	(23,130)	(22,720)	(23,645)
Principal payments on construction loan financings	(2,177)	(3,428)	(30,383)
Proceeds from mortgage/construction loan financings	14,776	20,346	13,960
Proceeds from (repayment of)/borrowings under unsecured revolving credit facilities, net	8,559	112,137	(11,309)
Repayment of unsecured term loan/notes	(215,900)	(92,600)	(471,725)
Proceeds from issuance of unsecured term loan/notes	400,000		449,720
Financing origination costs	(2,138)	(11,478)	(5,330)
Redemption of/distribution to noncontrolling interests	(42,315)	(26,682)	(80,852)
Dividends paid	(382,722)	(353,764)	(306,964)
Cash retained from excess tax benefits			103
Proceeds from issuance of stock	796,748	6,537	177,837
Redemption of preferred stock	(635,000)
Repurchase of common stock	(30,947)	(6,003)
Net cash flow used for financing activities	(399,061)	(440,125)	(514,743)
Change in cash and cash equivalents	28,993	(12,272)	3,096
Cash and cash equivalents, beginning of period	112,882	125,154	122,058
Cash and cash equivalents, end of period	141,875	112,882	125,154
Interest paid during the period (net of capitalized interest of $1,538, $7,086, and $14,730 respectively)	226,775	220,270	242,033
Income taxes paid during the period	$ 2,122	$ 2,606	$ 3,278