Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Cash flows from operating activities:
Net income	$ 27,241	$ 12,507
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of marketable securities	0	(4,543)
Co-investments	862	1,445
Amortization expense	2,871	2,884
Amortization of discount on marketable securities	(1,256)	(1,133)
Amortization of discount on notes receivables	(466)	(329)
Gain on the sales of real estate	(10,870)	0
Depreciation	40,828	37,031
Equity-based compensation	986	427
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,563)	(1,011)
Accounts payable and accrued liabilities	14,610	9,281
Other liabilities	(83)	748
Net cash provided by operating activities	72,160	57,307
Additions to real estate:
Acquisitions of real estate	(38,900)	(31,400)
Improvements to recent acquisitions	(2,296)	(8,881)
Redevelopment	(8,008)	(6,347)
Revenue generating capital expenditures	(611)	0
Non-revenue generating capital expenditures	(1,200)	(2,933)
Acquisition of and additions to real estate under development	(6,789)	(29,171)
Dispositions of real estate	16,816	0
Changes in restricted cash and refundable deposits	517	1,136
Purchases of marketable securities	(5,438)	(6,805)
Sales and maturities marketable securities	1,348	26,798
Collections of notes and other receivables	7,164	184
Contributions to co-investments	(12,945)	(26,767)
Distributions from co-investments	6,291	0
Net cash used in investing activities	(44,051)	(84,186)
Cash flows from financing activities:
Borrowings under debt agreements	159,394	304,187
Repayment of debt	(177,984)	(191,542)
Additions to deferred charges	(293)	(474)
Payments to settle derivative instruments	0	(2,395)
Equity related issuance cost	(150)	0
Net proceeds from stock options exercised	933	1,361
Net proceeds from issuance of common stock	31,590	38,436
Distributions to noncontrolling interest	(3,850)	(5,028)
Redemption of noncontrolling interest	(435)	(741)
Common and preferred stock dividends paid	(36,459)	(32,995)
Net cash (used in) provided by financing activities	(27,254)	110,809
Net (decrease) increase in cash and cash equivalents	855	83,930
Cash and cash equivalents at beginning of year	12,889	13,753
Cash and cash equivalents at end of year	13,744	97,683
Supplemental disclosure of cash flow information:
Cash paid for interest, net of $1,616, and $2,182 capitalized in 2012 and 2011, respectively	22,603	24,161
Supplemental disclosure of noncash investing and financing activities:
Transfer from real estate under development to rental properties	242	41,730
Contribution of note receivable to co-investment	12,325	0
Change in accrual of dividends	2,484	530
Change in fair value of derivative liabilities	396	2,334
Change in fair value of marketable securities	379	3,214
Change in construction payable	$ 3,168	$ 1,429