Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income	$ 135,153	$ 89,950
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of marketable securities	(1,767)	(521)
Gain on remeasurement of co-investment	0	(21,947)
Company's share of gain on the sales of co-investment	(41,252)	0
Gain on the sales of real estate	(14,161)	(10,870)
(Gain) loss on early retirement of debt	(846)	2,661
Co-investments	(1,892)	5,141
Amortization expense	8,955	8,681
Amortization of discount on notes receivables	(844)	(1,373)
Amortization of discount on marketable securities	(4,664)	(3,808)
Depreciation	143,662	125,669
Equity-based compensation	3,137	2,880
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(19,689)	(3,653)
Accounts payable and accrued liabilities	19,091	26,167
Other liabilities	199	358
Net cash provided by operating activities	225,082	219,335
Additions to real estate:
Acquisitions of real estate	(205,539)	(157,011)
Improvements to recent acquisitions	(14,374)	(6,662)
Redevelopment	(32,488)	(31,277)
Revenue generating capital expenditures	(2,165)	(4,405)
Lessor required capital expenditure	(4,320)	0
Non-revenue generating capital expenditures	(21,885)	(15,776)
Acquisitions of and additions to real estate under development	(13,963)	(22,505)
Acquisition of membership interest in co-investment	0	(85,000)
Dispositions of real estate	33,666	27,800
Changes in restricted cash and deposits	(17,246)	(13,370)
Purchases of marketable securities	(16,442)	(73,735)
Sales and maturities of marketable securities	22,830	6,322
Purchases of and advances under notes and other receivables	(56,750)	0
Collections of notes and other receivables	53,438	7,977
Contributions to co-investments	(150,852)	(158,769)
Distributions from co-investments	117,103	8,345
Net cash used in investing activities	(308,987)	(518,066)
Cash flows from financing activities:
Borrowings under debt agreements	641,892	1,347,973
Repayment of debt	(536,926)	(1,196,977)
Additions to deferred charges	(3,836)	(6,415)
Equity related issuance cost	(616)	(309)
Net proceeds from stock options exercised	4,756	2,169
Net proceeds from issuance of common stock	122,905	268,858
Contributions from noncontrolling interest	0	2,400
Distributions to noncontrolling interest	(14,108)	(12,875)
Redemption of noncontrolling interest	(5,113)	(1,595)
Common and preferred stock dividends paid	(134,146)	(115,444)
Net cash provided by financing activities	74,808	287,785
Net decrease in cash and cash equivalents	(9,097)	(10,946)
Cash and cash equivalents at beginning of year	18,606	12,889
Cash and cash equivalents at end of period	9,509	1,943
Supplemental disclosure of cash flow information:
Cash paid for interest, net of $12.7 million, and $6.8 million capitalized in 2013 and 2012, respectively	76,596	68,555
Supplemental disclosure of noncash investing and financing activities:
Transfer from real estate under development to rental properties	68	5,648
Transfer from real estate under development to co-investments	27,906	148,053
Mortgage notes assumed in connection with purchases of real estate including the loan premiums recorded	0	71,340
Contribution of note receivable to co-investment	0	12,325
Change in accrual of dividends	5,434	4,766
Change in fair value of derivative liabilities	3,649	5,100
Change in fair value of marketable securities	2,958	4,542
Change in construction payable	$ 1,544	$ 2,239