CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash flows from operating activities:
Net (loss) income	$ (14,262)	[1]	$ 37,213	[1]	$ (42,550)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation	135,095		133,162		128,204
Amortization	9,505		12,903		15,951
Straight-line rent adjustments	(1,467)		(1,425)		(2,234)
Provision for doubtful accounts	1,566		1,656		1,861
Amortization of deferred compensation	8,455		8,071		11,028
Loss on hedge ineffectiveness	1,761		3,409		0
Gain on sales of real estate and discontinued operations	(14,473)		(78,512)		(947)
Equity in income of partnerships in excess of distributions	(1,675)		(2,713)		0
Amortization of historic tax credits	(2,508)		(2,494)		(1,810)
Impairment of assets and expensed project costs	20,187		30,775		5,057
Change in assets and liabilities:
Net change in other assets	3,921		(7,779)		(15,167)
Net change in other liabilities	(1,030)		1,953		20,931
Net cash provided by operating activities	145,075		136,219		120,324
Cash flows from investing activities:
Cash proceeds from sales of real estate investments	190,442		181,644		0
Investments in consolidated real estate acquisitions	(20,000)		(60,879)		0
Additions to construction in progress	(41,512)		(36,456)		(38,104)
Investments in real estate improvements	(71,346)		(44,785)		(43,543)
Additions to leasehold improvements	(1,656)		(2,062)		(881)
Investments in partnerships	(19,184)		(250)		(3,682)
Capitalized leasing costs	(5,446)		(5,261)		(5,336)
Increase in cash escrows	(2,369)		(2,682)		(1,404)
Cash distributions from partnerships in excess of equity in income	2,721		1,472		4,772
Net cash provided by (used in) investing activities	31,650		30,741		(88,178)
Cash flows from financing activities:
Borrowings from (repayments of) term loans	(130,000)		(182,000)		(58,000)
Net (repayments of) borrowings from revolving facilities	(130,000)		130,000		(95,000)
Proceeds from mortgage loans	0		154,692		467,750
Repayment of mortgage loans	(76,784)		(403,691)		(320,731)
Principal installments on mortgage loans	(17,919)		(16,973)		(20,311)
Payment of deferred financing costs	(1,918)		(4,035)		(1,753)
Net proceeds from issuance of common shares in public offering	0		220,511		0
Common shares issued	3,270		2,983		1,788
Repayment of Exchangeable Notes	0		0		(136,900)
Dividends paid to common shareholders	(54,988)		(48,315)		(35,735)
Dividends paid to preferred shareholders	(15,848)		(15,849)		(7,324)
Distributions paid to Operating Partnership unit holders and noncontrolling interest	(1,703)		(1,626)		(1,459)
Value of shares issued under equity incentive plans, net of shares retired	(4,632)		(2,417)		(6,510)
Net cash used in financing activities	(170,522)		(166,720)		(19,954)
Net change in cash and cash equivalents	6,203		240		12,192
Cash and cash equivalents, beginning of year	34,230		33,990		21,798
Cash and cash equivalents, end of year	40,433		34,230		33,990
Series A [Member]
Cash flows from financing activities:
Net proceeds from issuance of preferred shares	0		0		110,896
Series B [Member]
Cash flows from financing activities:
Net proceeds from issuance of preferred shares	$ 0		$ 0		$ 83,335

[1] Includes gains on sales of discontinued operations (before non controlling interest) of $33.4 million (1st Quarter 2013), $45.1 million (3rd Quarter 2013).