Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Schedule of Fair Values of Financial Assets and Liabilities by Levels [Table Text Block]

(Amounts in thousands)		As of September 30, 2015
		Total		Level 1		Level 2		Level 3
Marketable securities		$	152,927	$	152,927	$	-	$	-
Real estate fund investments (75% of which is attributable to
	noncontrolling interests)		555,414		-		-		555,414
Deferred compensation plan assets (included in other assets)			117,037		48,829		-		68,208
	Total assets	$	825,378	$	201,756	$	-	$	623,622
Mandatorily redeemable instruments (included in other liabilities)		$	53,135	$	53,135	$	-	$	-
Interest rate swap (included in other liabilities)			24,014		-		24,014		-
	Total liabilities	$	77,149	$	53,135	$	24,014	$	-
(Amounts in thousands)		As of December 31, 2014
		Total		Level 1		Level 2		Level 3
Marketable securities		$	206,323	$	206,323	$	-	$	-
Real estate fund investments (75% of which is attributable to
	noncontrolling interests)		513,973		-		-		513,973
Deferred compensation plan assets (included in other assets)			117,284		53,969		-		63,315
	Total assets	$	837,580	$	260,292	$	-	$	577,288
Mandatorily redeemable instruments (included in other liabilities)		$	55,097	$	55,097	$	-	$	-
Interest rate swap (included in other liabilities)			25,797		-		25,797		-
	Total liabilities	$	80,894	$	55,097	$	25,797	$	-

Non-financial Assets Measured at Fair Value on a Nonrecurring Basis [Table Text Block]

(Amounts in thousands)	As of December 31, 2014
	Total		Level 1		Level 2		Level 3
Real estate assets	$	4,848	$	-	$	-	$	4,848

Schedule Of Carrying Amounts And Fair Values Of Financial Instruments [Table Text Block]

(Amounts in thousands)		As of September 30, 2015				As of December 31, 2014
		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value
Cash equivalents		$	545,617	$	546,000	$	749,418	$	749,000
Mortgage and mezzanine loans receivable
	(included in other assets)		-		-		16,748		17,000
		$	545,617	$	546,000	$	766,166	$	766,000
Debt:
	Mortgages payable	$	9,159,413	$	9,272,000	$	8,263,165	$	8,224,000
	Senior unsecured notes		847,594		884,000		1,347,159		1,385,000
	Revolving credit facility debt		-		-		-		-
		$	10,007,007	$	10,156,000	$	9,610,324	$	9,609,000

Real Estate Fund [Member]

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Fair Value Inputs, Assets, Quantitative Information [Table Text Block]

				Weighted Average
		Range		(based on fair value of investments)
Unobservable Quantitative Input		September 30, 2015	December 31, 2014	September 30, 2015	December 31, 2014
	Discount rates	12.0% to 14.5%	12.0% to 17.5%	13.2%	13.7%
	Terminal capitalization rates	4.8% to 6.5%	4.7% to 6.5%	5.5%	5.3%

Summary of Changes in Level 3 Plan Assets [Table Text Block]

(Amounts in thousands)	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
		2015		2014	2015		2014
Beginning balance	$	565,976	$	549,091	$	513,973	$	667,710
Purchases		11		725		95,011		3,392
Dispositions / distributions		(8,029)		(74,755)		(91,450)		(307,268)
Net unrealized (losses) gains		(2,544)		18,333		37,001		55,221
Net realized (losses) gains		(907)		1,998		1,405		76,337
Other, net		907		-		(526)		-
Ending balance	$	555,414	$	495,392	$	555,414	$	495,392

Deferred Compensation Plan Assets [Member]

Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]

Summary of Changes in Level 3 Plan Assets [Table Text Block]

(Amounts in thousands)	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
		2015		2014	2015		2014
Beginning balance	$	67,668	$	64,609	$	63,315	$	68,782
Purchases		2,153		1,377		8,384		10,936
Sales		(171)		(4,917)		(5,264)		(21,296)
Realized and unrealized (loss) gain		(1,466)		927		1,256		2,901
Other, net		24		1,187		517		1,860
Ending balance	$	68,208	$	63,183	$	68,208	$	63,183