Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating activities:
Net income (loss)	$ 21,390	$ 41,733
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Non-cash impairment charges	12,042	0
Loss (income) from discontinued operations	547	(17,599)
Costs associated with loan refinancing or payoff, net (non-cash portion)	0	1,759
Equity in income from joint ventures	(47)	(774)
Distributions from joint ventures	354	652
Depreciation and amortization	12,457	11,871
Amortization of deferred financing costs	1,085	1,023
Share-based compensation expense to management and trustees	1,464	1,367
Increase in restricted cash	1,450	740
Increase in mortgage notes accrued interest receivable	(13)	0
Decrease (increase) in accounts receivable, net	(390)	(1,440)
Decrease in notes receivable and accrued interest receivable	26	23
Increase in direct financing lease receivable	(1,256)	(1,255)
Increase in other assets	(3,171)	(1,261)
Increase (decrease) in accounts payable and accrued liabilities	(6,768)	(4,945)
Increase (decrease) in unearned rents	2,628	33
Net operating cash provided by continuing operations	41,798	31,927
Net operating cash provided by discontinued operations	161	3,077
Net cash provided by operating activities	41,959	35,004
Investing activities:
Acquisition of rental properties and other assets	(31,507)	(38,628)
Investment in unconsolidated joint ventures	(442)	(2,746)
Investment in mortgage notes receivable	(24,451)	(1,524)
Investment in direct financing lease, net	0	(2,113)
Additions to properties under development	(13,672)	(2,668)
Net cash used by investing activities of continuing operations	(70,072)	(47,679)
Net cash used by other investing activities of discontinued operations	0	(58)
Net proceeds from sale of real estate from discontinued operations	282	205,176
Net cash provided (used) by investing activities	(69,790)	157,439
Financing activities:
Proceeds from long-term debt facilities	320,000	163,000
Principal payments on long-term debt	(251,328)	(310,305)
Deferred financing fees paid	(1,852)	(619)
Net proceeds from issuance of common shares	56	66
Impact of stock option exercises, net	(480)	(499)
Purchase of common shares for treasury	(3,209)	(3,070)
Dividends paid to shareholders	(38,681)	(37,778)
Net cash provided (used) by financing activities	24,506	(189,205)
Effect of exchange rate changes on cash	174	150
Net increase (decrease) in cash and cash equivalents	(3,151)	3,388
Cash and cash equivalents at beginning of the year	14,625	11,776
Cash and cash equivalents at end of the year	11,474	15,164
Supplemental schedule of non-cash activity:
Transfer of property under development to rental property	1,038	0
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	6,694	6,283
Conversion of equity to mortgage loan related to atlantic-EPR I	14,852	0
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	21,845	23,567
Cash paid (received) during the year for income taxes	$ 197	$ 375