Real Estate (Summary of Real Estate Subject to Operating Leases) (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property Subject to or Available for Operating Lease [Line Items]
Real Estate Subject to Operating Leases, Gross	$ 5,200,475,000	$ 4,614,439,000
Less accumulated depreciation and amortization	(511,703,000)	(415,774,000)
Real estate subject to operating leases before work in process	4,688,772,000	4,198,665,000
Work in progress	28,908,000us-gaap_DevelopmentInProcess	60,720,000us-gaap_DevelopmentInProcess	86,579,000us-gaap_DevelopmentInProcess
Real estate subject to operating leases, net	4,717,680,000us-gaap_RealEstateInvestmentPropertyNet	4,259,384,000us-gaap_RealEstateInvestmentPropertyNet
Revenue recognized	1,521,000us-gaap_StraightLineRentAdjustments	(338,000)us-gaap_StraightLineRentAdjustments	487,000us-gaap_StraightLineRentAdjustments
Allowances	3,086,000nnn_DeferredRevenueLeasesAllowances	3,181,000nnn_DeferredRevenueLeasesAllowances
Balance of accrued rental income	25,659,000us-gaap_DeferredRevenueLeasesNet	24,797,000us-gaap_DeferredRevenueLeasesNet
Land and improvements
Property Subject to or Available for Operating Lease [Line Items]
Land and improvements	1,784,494,000	1,652,304,000
Buildings and improvements
Property Subject to or Available for Operating Lease [Line Items]
Buildings and improvements	3,414,691,000	2,960,845,000
Leasehold interests
Property Subject to or Available for Operating Lease [Line Items]
Leasehold interests	1,290,000	1,290,000
Work in progress
Property Subject to or Available for Operating Lease [Line Items]
Work in progress	$ 28,908,000	$ 60,719,000

Deferred Revenue, Leases, Allowances

No definition available.

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- Definition

Aggregate carrying amounts as of the balance sheet date of investments in leasehold interests

+ References

No definition available.

+ Details

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- Definition

Real Estate Subject To Operating Leases Before Work In Process

+ References

No definition available.

+ Details

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- Definition

Real Estate Subject to Operating Leases, Gross

+ References

No definition available.

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- Definition

This element represents revenue received, but not recognized for financial reporting purposes. Such deferred revenue may consist of and include amounts paid in advance by lessees and is net of the accumulated amortization of such amounts that to date have been recognized in revenue.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.15)

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- Definition

The current amount of expenditures for a real estate project that has not yet been completed.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.10)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Aggregate of the carrying amounts as of the balance sheet date of investments in building and building improvements.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(d))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Amount before accumulated depletion of real estate held for productive use, excluding land held for sale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 4

-Subparagraph (e)

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The amount of accumulated depreciation, by major property class, recorded on property subject to or available for lease as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6453916&loc=d3e41460-112716

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-Section 50

-Paragraph 4

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+ Details

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- Definition

Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1(d))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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- Definition

Amount of the adjustment to rental revenues to measure escalating leasing revenues on a straight line basis.

+ References

No definition available.

+ Details

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