Identified Intangible Assets and Intangible Liabilities (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Finite-Lived Intangible Assets And Liabilities [Line Items]
Gross amount	$ 429,909		$ 424,976
Accumulated amortization	(200,330)		(199,821)
Net	229,579us-gaap_FiniteLivedIntangibleAssetsNet		225,155us-gaap_FiniteLivedIntangibleAssetsNet
Gross amount	620,891		657,976
Accumulated amortization	(304,929)		(329,775)
Net	315,962		328,201
Below Market Leases Net Of Above Market Leases [Member]
Finite-Lived Intangible Assets And Liabilities [Line Items]
Amortization of Intangible Assets	12,450	9,712
2016	36,804
2017	34,829
2018	33,546
2019	23,514
2020	21,505
Other Identified Intangible Assets [Member]
Finite-Lived Intangible Assets And Liabilities [Line Items]
Amortization of Intangible Assets	6,185	8,891
2016	22,523
2017	17,692
2018	13,373
2019	11,425
2020	10,651
Tenant Under Ground Leases [Member]
Finite-Lived Intangible Assets And Liabilities [Line Items]
Amortization of Intangible Assets	458	458
2016	1,832
2017	1,832
2018	1,832
2019	1,832
2020	$ 1,832

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

Name:	us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References