Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net income (loss)	$ 115,292	$ (53,387)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of buildings and tenant improvements	214,118	193,479
Amortization of deferred leasing and other costs	89,359	86,859
Amortization of deferred financing costs	9,913	9,878
Straight-line rent adjustment	(12,421)	(15,725)
Asset impairment charges	3,777	0
Gain on acquisitions	(962)	0
Gains on land and depreciated property sales	(105,525)	(11,424)
Third-party construction contracts, net	27,117	(4,295)
Other accrued revenues and expenses, net	11,367	(14,621)
Operating distributions received in excess of (less than) equity in earnings from unconsolidated companies	(34,411)	10,772
Net cash provided by operating activities	317,624	201,536
Cash flows from investing activities:
Development of real estate investments	(320,698)	(176,340)
Acquisition of real estate investments and related intangible assets	(372,934)	(321,099)
Acquisition of undeveloped land	(30,101)	(37,166)
Second generation tenant improvements, leasing costs and building improvements	(60,052)	(46,682)
Other deferred leasing costs	(26,647)	(22,727)
Other assets	(14,725)	674
Proceeds from land and depreciated property sales, net	330,740	112,559
Capital distributions from unconsolidated companies	106,306	4,890
Capital contributions and advances to unconsolidated companies	(38,959)	(19,262)
Net cash provided by (used for) investing activities	(427,070)	(505,153)
Cash flows from financing activities:
Proceeds from issuance of common shares, net	632,531	236,301
Payments for redemption of preferred shares/units	(177,955)	(168,272)
Proceeds from unsecured debt	500,000	600,000
Payments on unsecured debt	(426,462)	(172,374)
Proceeds from secured debt financings	1,933	13,305
Payments on secured indebtedness including principal amortization	(112,097)	(107,240)
Borrowings (payments) on lines of credit, net	(75,000)	(20,293)
Dividends/Distributions to common shareholders/unitholders	(164,811)	(135,083)
Dividends/Distributions to preferred shareholders/unitholders	(24,261)	(31,630)
Contributions from (distributions to) noncontrolling interests, net	(2,692)	2,788
Buyout of noncontrolling interests	0	(6,208)
Change in book overdrafts	(44,225)	0
Deferred financing costs	(7,292)	(8,334)
Net cash provided by (used for) financing activities	99,669	202,960
Net increase (decrease) in cash and cash equivalents	(9,777)	(100,657)
Cash and cash equivalents at beginning of period	33,889	213,809
Cash and cash equivalents at end of period	24,112	113,152
Noncash investing and financing activities:
Assumption of indebtedness and other liabilities in real estate acquisitions	106,555	19,992
Carrying amount of pre-existing ownership interest in acquired property	630	0
Conversion of Limited Partner Units to common shares	338	29,002
Preferred distributions declared but not paid	0	3,726
Subsidiary of Common Parent [Member]
Cash flows from operating activities:
Net income (loss)	115,292	(53,387)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation of buildings and tenant improvements	214,118	193,479
Amortization of deferred leasing and other costs	89,359	86,859
Amortization of deferred financing costs	9,913	9,878
Straight-line rent adjustment	(12,421)	(15,725)
Asset impairment charges	3,777	0
Gain on acquisitions	(962)	0
Gains on land and depreciated property sales	(105,525)	(11,424)
Third-party construction contracts, net	27,117	(4,295)
Other accrued revenues and expenses, net	11,405	(14,582)
Operating distributions received in excess of (less than) equity in earnings from unconsolidated companies	(34,411)	10,772
Net cash provided by operating activities	317,662	201,575
Cash flows from investing activities:
Development of real estate investments	(320,698)	(176,340)
Acquisition of real estate investments and related intangible assets	(372,934)	(321,099)
Acquisition of undeveloped land	(30,101)	(37,166)
Second generation tenant improvements, leasing costs and building improvements	(60,052)	(46,682)
Other deferred leasing costs	(26,647)	(22,727)
Other assets	(14,725)	674
Proceeds from land and depreciated property sales, net	330,740	112,559
Capital distributions from unconsolidated companies	106,306	4,890
Capital contributions and advances to unconsolidated companies	(38,959)	(19,262)
Net cash provided by (used for) investing activities	(427,070)	(505,153)
Cash flows from financing activities:
Contributions from the General Partner	632,531	236,301
Payments for redemption of preferred shares/units	(177,955)	(168,272)
Proceeds from unsecured debt	500,000	600,000
Payments on unsecured debt	(426,462)	(172,374)
Proceeds from secured debt financings	1,933	13,305
Payments on secured indebtedness including principal amortization	(112,097)	(107,240)
Borrowings (payments) on lines of credit, net	(75,000)	(20,293)
Dividends/Distributions to common shareholders/unitholders	(167,092)	(137,662)
Dividends/Distributions to preferred shareholders/unitholders	(24,261)	(31,630)
Contributions from (distributions to) noncontrolling interests, net	(449)	5,311
Buyout of noncontrolling interests	0	(6,208)
Change in book overdrafts	(44,225)	0
Deferred financing costs	(7,292)	(8,334)
Net cash provided by (used for) financing activities	99,631	202,904
Net increase (decrease) in cash and cash equivalents	(9,777)	(100,674)
Cash and cash equivalents at beginning of period	33,889	213,826
Cash and cash equivalents at end of period	24,112	113,152
Noncash investing and financing activities:
Assumption of indebtedness and other liabilities in real estate acquisitions	106,555	19,992
Carrying amount of pre-existing ownership interest in acquired property	630	0
Conversion of Limited Partner Units to common shares	338	29,002
Preferred distributions declared but not paid	$ 0	$ 3,726