Notes Payable (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 derivatives	Dec. 31, 2011	Dec. 31, 2012 2014 Notes [Member]		Jun. 30, 2004 2014 Notes [Member]	Dec. 31, 2012 2015 Notes [Member]		Dec. 31, 2012 2017 Notes [Member]		Sep. 30, 2007 2017 Notes [Member]	Dec. 31, 2012 2021 Notes [Member]		Jul. 31, 2011 2021 Notes [Member] derivative	Dec. 31, 2012 Notes Payable Issued August 2012 [Member]		Jun. 30, 2012 Two Thousand Twelve Notes [Member]
Notes Payable [Line Items]
Principal			$ 150,000,000	[1],[2],[3]		$ 150,000,000	[1]	$ 250,000,000	[1],[4]		$ 300,000,000	[1],[5]		$ 325,000,000	[1]	$ 50,000,000
Discount	9,338,000	5,033,000	440,000	[1],[2],[3],[6]		390,000	[1],[6]	877,000	[1],[4],[6]		4,269,000	[1],[5],[6]		4,989,000	[1],[6]
Net Price			149,560,000	[1],[2],[3]		149,610,000	[1]	249,123,000	[1],[4]		295,731,000	[1],[5]		320,011,000	[1]
Stated Rate			6.25%	[1],[2],[3]		6.15%	[1]	6.875%	[1],[4]		5.50%	[1]		3.80%	[1]	7.75%
Effective Rate			5.91%	[1],[2],[3],[7]		6.185%	[1],[7]	6.924%	[4],[7]		5.69%	[1],[5],[7]		3.984%	[1],[7]
Derivative, Fixed Interest Rate					4.61%
Notional amount					94,000,000					100,000,000			150,000,000
Liability amount from termination of hedge agreement										3,260,000			5,300,000
Liability amount from termination of hedge agreement, comprehensive income					4,148,000					3,228,000			5,218,000
Number of Interest Rate Derivatives Held	0												2
Debt Issuance Costs Incurred	$ 10,410,000

[1] The proceeds from the note issuance were used to pay down outstanding indebtedness of NNN’s Credit Facility.

[2] NNN entered into a forward starting interest rate swap agreement which fixed a swap rate of 4.61% on a notional amount of $94,000. Upon issuance of the 2014 Notes, NNN terminated the forward starting interest rate swap agreement resulting in a gain of $4,148. The gain has been deferred and is being amortized as an adjustment to interest expense over the term of the 2014 Notes using the effective interest method.

[3] The proceeds from the note issuance were used to repay the obligation of the 2004 Notes.

[4] NNN entered into an interest rate hedge with a notional amount of $100,000. Upon issuance of the 2017 Notes, NNN terminated the interest rate hedge agreement resulting in a liability of $3,260, of which $3,228 was recorded to other comprehensive income. The liability has been deferred and is being amortized as an adjustment to interest expense over the term of the 2017 Notes using the effective interest method.

[5] NNN entered into two interest rate hedges with a total notional amount of $150,000. Upon issuance of the 2021 Notes, NNN terminated the interest rate hedge agreements resulting in a liability of $5,300, of which $5,218 was deferred in other comprehensive income. The deferred liability is being amortized over the term of the note using the effective interest method.

[6] The note discounts are amortized to interest expense over the respective term of each debt obligation using the effective interest method.

[7] Includes the effects of the discount, treasury lock gain and swap gain (as applicable).