Condensed Consolidated Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 29,703	$ 27,241
Adjustments to reconcile net income to net cash provided by operating activities:
Gain on sale of marketable securities	(1,767)	0
Co-investments	(391)	862
Amortization expense	2,930	2,871
Amortization of discount on notes receivables	(844)	(466)
Amortization of discount on marketable securities	(1,377)	(1,256)
Gain on the sales of real estate	(1,503)	(10,870)
Depreciation	47,144	40,828
Equity-based compensation	1,132	986
Changes in operating assets and liabilities:
Prepaid expenses and other assets	1,764	(2,563)
Accounts payable and accrued liabilities	8,443	14,610
Other liabilities	458	(83)
Net cash provided by operating activities	85,692	72,160
Additions to real estate:
Acquisitions of real estate	(175,950)	(38,900)
Improvements to recent acquisitions	(2,601)	(2,296)
Redevelopment	(6,573)	(8,008)
Revenue generating capital expenditures	(304)	(611)
Non-revenue generating capital expenditures	(4,019)	(1,200)
Lessor required capital expenditure	(768)	0
Acquisitions of and additions to real estate under development	(3,332)	(6,789)
Dispositions of real estate	9,051	16,816
Changes in restricted cash deposits	19,980	517
Purchases of marketable securities	(6,541)	(5,438)
Sales and maturities of marketable securities	20,335	1,348
Collections of notes and other receivables	52,473	7,164
Contributions to co-investments	(45,518)	(12,945)
Distributions from co-investments	38,030	6,291
Net cash used in investing activities	(105,737)	(44,051)
Cash flows from financing activities:
Borrowings under debt agreements	235,282	159,394
Repayment of debt	(279,854)	(177,984)
Additions to deferred charges	(716)	(293)
Equity related issuance cost	(225)	(150)
Net proceeds from stock options exercised	1,367	933
Net proceeds from issuance of common stock	122,905	31,590
Distributions to noncontrolling interest	(3,995)	(3,850)
Redemption of noncontrolling interest	(1,329)	(435)
Common and preferred stock dividends paid	(41,152)	(36,459)
Net cash provided by (used in) financing activities	32,283	(27,254)
Net increase in cash and cash equivalents	12,238	855
Cash and cash equivalents at beginning of year	18,606	12,889
Cash and cash equivalents at end of period	30,844	13,744
Supplemental disclosure of cash flow information:
Cash paid for interest, net of $3.7 million, and $1.6 million capitalized in 2013 and 2012, respectively	23,863	22,603
Supplemental disclosure of noncash investing and financing activities:
Transfer from real estate under development to rental properties	67	242
Contribution of note receivable to co-investment	0	12,325
Change in accrual of dividends	5,344	2,484
Change in fair value of derivative liabilities	570	396
Change in fair value of marketable securities	1,629	379
Change in construction payable	$ 3,376	$ 3,168