Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities:
Net income (loss)	$ 115,266	$ 113,055	$ (11,906)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Provision for loan losses	0	700	70,954
Non-cash impairment charges	27,115	463	2,083
Loss (income) from discontinued operations	(12,703)	4,178	46,430
Costs associated with loan refinancing or payoff, net (non-cash portion)	1,759	3,067	117
Equity in income from joint ventures	(2,847)	(2,138)	(895)
Distributions from joint ventures	2,848	2,482	986
Depreciation and amortization	47,927	45,359	41,401
Amortization of deferred financing costs	3,807	4,408	3,663
Share-based compensation expense to management and trustees	5,610	4,710	4,307
Increase in restricted cash	(652)	(1,961)	(148)
Increase in mortgage notes accrued interest receivable	(5)	(828)	(1,324)
Decrease (increase) in accounts receivable, net	606	(5,547)	1,243
Decrease in notes receivable and accrued interest receivable	112	53	530
Increase in direct financing lease receivable	(5,073)	(4,750)	(3,762)
Increase in other assets	(591)	(3,084)	(3,354)
Increase (decrease) in accounts payable and accrued liabilities	4,043	11,859	(1,353)
Increase (decrease) in unearned rents	66	(465)	(1,339)
Net operating cash provided by continuing operations	187,288	171,561	147,633
Net operating cash provided by discontinued operations	8,511	8,830	1,184
Net cash provided by operating activities	195,799	180,391	148,817
Investing activities:
Acquisition of rental properties and other assets	(53,175)	(131,057)	(135,112)
Proceeds from sale of real estate	1,700	0	0
Investment in unconsolidated joint ventures	(3,970)	(16,691)	(1,677)
Cash paid related to Cappelli settlement	0	(4,586)	0
Investment in mortgage notes receivable	(19,688)	(5,696)	(35,945)
Proceeds from mortgage note receivable paydown	0	0	3,512
Investment in promissory notes receivable	0	0	(4,108)
Proceeds from promissory note receivable paydown	0	0	1,000
Investment in direct financing leases, net	(2,113)	(51,833)	0
Additions to properties under development	(57,926)	(4,934)	(19,672)
Net cash used by investing activities of continuing operations	(135,172)	(214,797)	(192,002)
Net cash used by other investing activities of discontinued operations	(58)	(112,977)	0
Net proceeds from sale of real estate from discontinued operations	224,912	7,456	0
Net cash provided (used) by investing activities	89,682	(320,318)	(192,002)
Financing activities:
Proceeds from long-term debt facilities	387,000	770,225	132,006
Principal payments on long-term debt	(425,859)	(616,494)	(266,423)
Deferred financing fees paid	(3,731)	(11,609)	(5,017)
Net proceeds from issuance of common shares	253	141,134	284,965
Redemption of preferred shares	(80,030)	0	0
Impact of stock option exercises, net	966	(815)	(805)
Proceeds from payment of shareholder loan	0	281	0
Purchase of common shares for treasury	(3,070)	(2,182)	(1,201)
Contributions (distributions) paid from (to) noncontrolling interests	0	10	(209)
Dividends paid to shareholders	(157,844)	(146,324)	(126,907)
Net cash provided (used) by financing activities of continuing operations	(282,315)	134,226	16,409
Net cash used by financing activities of discontinued operations	0	(6,271)	(751)
Net cash provided (used) by financing activities	(282,315)	127,955	15,658
Effect of exchange rate changes on cash	(317)	610	583
Net increase (decrease) in cash and cash equivalents	2,849	(11,362)	(26,944)
Cash and cash equivalents at beginning of the year	11,776	23,138	50,082
Cash and cash equivalents at end of the year	14,625	11,776	23,138
Supplemental schedule of non-cash activity:
Transfer of property under development to rental property	41,087	7,005	38,990
Acquisition of real estate in exchange for assumption of debt at fair value	4,109	0	0
Issuance of nonvested shares and restricted share units at fair value, including nonvested shares issued for payment of bonuses	6,785	4,718	4,368
Receipt of 86,056 common shares in payment of shareholder loans	0	3,261	0
Supplemental disclosure of cash flow information:
Cash paid during the year for interest	69,368	63,096	70,124
Cash paid (received) during the year for income taxes	$ 40	$ 469	$ (383)