Disposition of Investment Property and Discontinued Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Disposal Groups, Including Discontinued Operations Disclosure [Abstract]
Sales price of real estate	$ 44,200npi6_Salespriceofrealestate
Net proceeds from sale of discontinued operations	43,210	0
Noncash Commission and Closing Costs	987
Gain from sale of discontinued operations	35,309	0
Payments of Debt Extinguishment Costs	22,530us-gaap_ExtinguishmentOfDebtAmount
Loss on extinguishment of debt	5,373
Prepayment Penalties Associated With Loans	$ 5,161

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Prepayment penalties associated with loans.

+ References

No definition available.

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- Definition

Sales price of real estate

+ References

No definition available.

+ Details

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- Definition

Amount of gain (loss), after tax expense or benefit and not previously recognized, resulting from the sale of a business component.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

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- Definition

Gross amount of debt extinguished.

+ References

No definition available.

+ Details

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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 470

-SubTopic 50

-Section 40

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12317-112629

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

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-Section 40

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6850294&loc=d3e12355-112629

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- Definition

The expense related to real estate commissions and closing costs that are not paid in cash. Is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.

+ References

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- Definition

Cash received from the sale of real estate that is held for investment, that is, it is part of an investing activity during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

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