Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Cash flows from operating activities
Net income	$ 293,900		$ 59,961		$ 31,142
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization, including discontinued operations	209,872		181,791		174,465
Gain on acquisition of controlling interest in joint ventures	(57,418)		0		0
Gain on sale of discontinued operations, net of tax	(115,068)		(24,621)		(9,614)
Gain on sale of properties, including land	0		(4,748)		(236)
Gain on sale of unconsolidated joint venture interests	0		(1,136)		0
Gain on sale of available-for-sale investment	0		(4,301)		0
Loss on discontinuation of hedging relationship	0		29,791		0
Impairment provision on technology investment	0		0		1,000
Distributions of income from joint ventures	6,321		5,329		6,524
Equity in (income) loss of joint ventures	(20,175)	[1]	(5,679)	[1]	839	[1]
Share-based compensation	13,086		12,039		11,306
Amortization of deferred financing costs	3,608		5,877		4,102
Net change in operating accounts	(9,859)		(9,469)		4,508
Net cash from operating activities	324,267		244,834		224,036
Cash flows from investing activities
Development and capital improvements	(290,728)		(227,755)		(63,739)
Acquisition of operating properties, including joint venture interests, net of cash acquired	(465,400)		0		0
Proceeds from sale of properties, including land and discontinued operations	226,869		57,312		102,819
Proceeds from sale of joint venture interests	0		19,310		0
Proceeds from sale of available-for-sale investment	0		4,510		0
Decrease in notes receivable - affiliates	0		3,279		637
Investments in joint ventures	(7,006)		(46,037)		(6,467)
Distributions of investments from joint ventures	17,417		6,005		28
Other	(8,837)		(3,988)		1,872
Net cash from investing activities	(527,685)		(187,364)		35,150
Cash flows from financing activities
Borrowings on unsecured line of credit	603,000		8,000		37,000
Repayments on unsecured line of credit	(603,000)		(8,000)		(37,000)
Repayment of notes payable	(567,575)		(627,623)		(306,692)
Proceeds from notes payable	346,308		495,705		57,748
Proceeds from issuance of common shares	693,355		106,571		231,651
Redemption of perpetual preferred units	(100,000)		0		0
Distributions to common shareholders, perpetual preferred units, and non-controlling interests	(189,018)		(152,242)		(135,626)
Purchase of non-controlling interests	(16,482)		0		0
Payment of deferred financing costs	(3,737)		(9,288)		(6,564)
Common share options exercised	13,038		11,397		1,435
Net (increase) decrease in accounts receivable - affiliates	(2,586)		860		4,217
Other	1,625		1,734		1,064
Net cash from financing activities	174,928		(172,886)		(152,767)
Net increase (decrease) in cash and cash equivalents	(28,490)		(115,416)		106,419
Cash and cash equivalents, beginning of period	55,159		170,575		64,156
Cash and cash equivalents, end of period	26,669		55,159		170,575
Supplemental information
Cash paid for interest, net of interest capitalized	106,405		114,615		128,742
Cash paid for income taxes	1,561		2,664		1,169
Supplemental schedule of non-cash investing and financing activities
Distributions declared but not paid	49,969		39,364		35,295
Value of shares issued under benefit plans, net of cancellations	20,933		18,629		14,401
Conversion of operating partnership units to common shares	9,143		592		3,536
Accrual associated with construction and capital expenditures	18,993		16,754		6,590
Conversion of mezzanine notes to joint venture equity	0		0		43,279
Change of fair value of available-for-sale investments, net of tax	0		0		3,306
Acquisition of operating properties, including joint venture interests:
Real estate assets	0		0		238,885
In-place leases	0		0		4,962
Other assets	0		0		1,135
Mortgage debt assumed	298,807		0		188,119
Other liabilities	$ 6,976		$ 0		$ 3,197

[1] (3)Equity in income (loss) excludes our ownership interest of fee income from various property management services and interest income from mezzanine loans with our joint ventures.