Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Operating activities:
Net income (loss)	$ 58,208	$ 41,735
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Non-cash impairment charges	8,195	24,298
Loss (income) from discontinued operations	4,225	(7,152)
Costs associated with loan refinancing or payoff, net (non-cash portion)	0	1,759
Equity in income from joint ventures	324	1,555
Distributions from joint ventures	638	1,304
Depreciation and amortization	25,073	23,455
Amortization of deferred financing costs	2,177	1,787
Share-based compensation expense to management and trustees	2,998	2,841
Increase in restricted cash	1,851	1,649
Increase in mortgage notes accrued interest receivable	(37)	0
Decrease (increase) in accounts receivable, net	494	1,015
Decrease in notes receivable and accrued interest receivable	8	48
Increase in direct financing lease receivable	(2,538)	(2,553)
Increase in other assets	(1,051)	(1,874)
Increase (decrease) in accounts payable and accrued liabilities	(1,156)	2,927
Increase (decrease) in unearned rents	2,511	138
Net operating cash provided by continuing operations	101,272	89,822
Net operating cash provided by discontinued operations	2,168	2,508
Net cash provided by operating activities	103,440	92,330
Investing activities:
Acquisition of rental properties and other assets	(40,424)	(38,924)
Investment in unconsolidated joint ventures	(661)	(2,784)
Investment in mortgage notes receivable	(64,561)	(6,036)
Investment in direct financing lease, net	0	(2,113)
Additions to properties under development	(43,597)	(18,437)
Net cash used by investing activities of continuing operations	(149,243)	(68,294)
Net cash used by other investing activities of discontinued operations	0	(58)
Net proceeds from sale of real estate from discontinued operations	12,969	212,396
Net cash provided (used) by investing activities	(136,274)	144,044
Financing activities:
Proceeds from long-term debt facilities	396,000	195,000
Principal payments on long-term debt	(279,663)	(345,352)
Deferred financing fees paid	(2,101)	(934)
Net proceeds from issuance of common shares	133	145
Impact of stock option exercises, net	(480)	(499)
Purchase of common shares for treasury	(3,209)	(3,070)
Dividends paid to shareholders	(79,764)	(77,951)
Net cash provided (used) by financing activities	30,916	(232,661)
Effect of exchange rate changes on cash	32	251
Net increase (decrease) in cash and cash equivalents	(1,886)	3,964
Cash and cash equivalents at beginning of the year	14,625	11,776
Cash and cash equivalents at end of the year	12,739	15,740
Supplemental schedule of non-cash activity:
Transfer of property under development to rental property	22,702	4,552
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
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests	27,785	0
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	34,487	36,025
Cash paid (received) during the year for income taxes	$ (715)	$ 632