Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Net Income (Loss) Available to Common Stockholders, Diluted	$ 74,317	$ 52,379
Net Income Loss From Discontinuing Operation Available To Common Stockholders Diluted	(4,260)	7,089
Net Income Loss From Continuing Operation Available To Common Stockholders Diluted	78,577	45,290
Operating activities:
Net income (loss)	92,383	77,299
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Asset Impairment Charges	11,281	24,298
Loss (income) from discontinued operations	4,260	(7,089)
Costs associated with loan refinancing or payoff, net (non-cash portion)	439	1,759
Equity in income from joint ventures	666	2,231
Distributions from joint ventures	827	2,176
Depreciation and amortization	38,349	35,316
Amortization of deferred financing costs	3,224	2,821
Share-based compensation expense to management and trustees	4,416	4,211
Increase in restricted cash	(2,695)	1,225
Increase in mortgage notes accrued interest receivable	(828)	(410)
Decrease (increase) in accounts receivable, net	(1,820)	(58)
Decrease in notes receivable and accrued interest receivable	68	72
Increase in direct financing lease receivable	(3,730)	(3,795)
Increase in other assets	(2,063)	(1,797)
Increase (decrease) in accounts payable and accrued liabilities	(2,504)	(1,434)
Increase (decrease) in unearned rents	2,478	(124)
Net operating cash provided by continuing operations	143,419	132,239
Net operating cash provided by discontinued operations	1,984	3,212
Net cash provided by operating activities	145,403	135,451
Investing activities:
Acquisition of rental properties and other assets	(42,094)	(46,427)
Proceeds from Sale of Real Estate	0	1,700
Investment in unconsolidated joint ventures	(1,131)	(3,245)
Investment in mortgage notes receivable	(71,908)	(9,390)
Investment in direct financing lease, net	0	(2,118)
Proceeds from Sale of Lease Receivables	4,494	0
Additions to properties under development	(88,965)	(44,230)
Net cash used by investing activities of continuing operations	(199,604)	(103,710)
Net cash used by other investing activities of discontinued operations	0	(58)
Net proceeds from sale of real estate from discontinued operations	12,969	224,912
Net cash provided (used) by investing activities	(186,635)	121,144
Financing activities:
Proceeds from long-term debt facilities	798,000	328,000
Principal payments on long-term debt	(616,400)	(379,428)
Deferred financing fees paid	(5,797)	(1,002)
Net proceeds from issuance of common shares	179	195
Redemption of preferred shares	0	80,030
Impact of stock option exercises, net	(485)	966
Purchase of common shares for treasury	(3,232)	(3,070)
Dividends paid to shareholders	(120,856)	(119,164)
Net cash provided (used) by financing activities	51,409	(253,533)
Effect of exchange rate changes on cash	205	(536)
Net increase (decrease) in cash and cash equivalents	10,382	2,526
Cash and cash equivalents at beginning of the year	14,625	11,776
Cash and cash equivalents at end of the year	25,007	14,302
Supplemental schedule of non-cash activity:
Transfer of property under development to rental property	75,172	35,100
Acquisition of real estate in exchange for assumption of debt at fair value	0	4,109
Issuance of nonvested shares and restricted share units at fair value, including nonvested shares issued for payment of bonuses	7,181	6,785
Conversion of equity to mortgage loan related to atlantic-EPR I	14,852	0
noncash adjustment for redemption of noncontrolling interest	27,785	0
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	56,566	57,652
Cash paid (received) during the year for income taxes	$ (521)	$ (212)