Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flow from operating activities:
Net income	$ 232,889	$ 347,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	187,344	167,609
Impairment charges	31,336	58,053
Equity award expense	13,775	11,552
Gain on sale of operating properties	(21,569)	(72,101)
Gain on change in control of interests	(71,160)	(46,512)
Equity in income of joint ventures, net	(27,902)	(178,618)
Equity in income from other real estate investments, net	(42,043)	(18,758)
Distributions from joint ventures and other real estate investments	27,678	54,029
Change in accounts and notes receivable	4,916	2,551
Change in accounts payable and accrued expenses	(10,506)	(4,697)
Change in Canadian withholding tax receivable	(507)	(66,911)
Change in other operating assets and liabilities	(24,217)	(37,350)
Net cash flow provided by operating activities	300,034	215,847
Cash flow from investing activities:
Acquisition of operating real estate and other related net assets	(56,036)	(95,801)
Improvements to operating real estate	(81,280)	(70,333)
Acquisition of real estate under development	(10,010)	(50,778)
Improvements to real estate under development	(91,729)	(18,448)
Investment in marketable securities	(9,822)	(1,325)
Proceeds from sale of marketable securities	1,846	1,850
Investments in and advances to real estate joint ventures	(22,704)	(26,160)
Reimbursements of investments in and advances to real estate joint ventures	15,793	56,431
Distributions from liquidation of real estate joint ventures		136,005
Return of investment from liquidation of real estate joint ventures		149,296
Investment in other real estate investments	(569)	(233)
Reimbursements of investments and advances to other real estate investments	39,751	10,475
Collection of mortgage loans receivable	514	461
Reimbursements of other investments		500
Proceeds from sale of operating properties	66,803	214,858
Proceeds from sale of development properties		4,551
Net cash flow (used for)/provided by investing activities	(147,443)	311,349
Cash flow from financing activities:
Principal payments on debt, excluding normal amortization of rental property debt	(463,572)	(233,303)
Principal payments on rental property debt	(8,129)	(10,380)
Proceeds from unsecured revolving credit facility, net	449,958	100,019
Proceeds from issuance of unsecured notes	400,000	150,000
Repayments under unsecured term loan/notes	(250,000)	(300,000)
Financing origination costs	(14,936)	(4,697)
Payment of early extinguishment of debt charges	(708)
Change in tenants' security deposits	640	963
Contributions from noncontrolling interests	1,284
Conversion/distribution of noncontrolling interests	(14,695)	(2,572)
Dividends paid	(252,793)	(235,458)
Proceeds from issuance of stock, net	973	156,513
Net cash flow used for financing activities	(151,978)	(378,915)
Change in cash and cash equivalents	613	148,281
Cash and cash equivalents, beginning of period	142,486	189,534
Cash and cash equivalents, end of period	143,099	337,815
Interest paid during the period (net of capitalized interest of $6,442 and $3,762, respectively)	96,306	111,761
Income taxes paid during the period (net of refunds received of $2,082 and $18,723, respectively)	$ 1,325	$ 94,639