Subsequent Events (Details) (USD $)			3 Months Ended		1 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 2028 Notes [Member]		May 02, 2013 Subsequent Event [Member] 2028 Notes [Member]	Apr. 30, 2013 Unsecured Debt [Member] Subsequent Event [Member] 2023 Notes [Member]	Mar. 31, 2013 Forward Contracts [Member]	Apr. 30, 2013 Forward Contracts [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Principal amount of debt			$ 234,035,000	[1],[2],[3]		$ 350,000,000
Stated interest rate			5.125%	[1],[2],[3]		3.30%
Offering price, percentage						99.259%
Effective Interest Rate			7.192%	[1],[2],[3],[4]		3.388%
Notional amount of interest rate cash flow hedge derivatives							240,000,000	240,000,000
Interest rate cash flow hedge liability, fair value								3,156,000
Amount of cash flow hedge reported in AOCI								3,141,000
Conversion ratio					39.536
Principal amount of debt converted			0	[1],[2],[3]	91,000
Outstanding principal balance	$ 223,035,000	$ 238,572,000	$ 223,035,000	[1],[2],[3]	$ 222,944,000

[1] The conversion rate per $1 principal amount was 39.5149 shares of NNN’s common stock, which is equivalent to a conversion price of $25.3069 per share of common stock.

[2] NNN repurchased $11,000 in 2009 for a purchase price of $8,588 resulting in a gain of $1,867.

[3] Debt issuance costs include underwriting discounts and commissions, legal and accounting fees, rating agency fees and printing expenses. These costs have been deferred and are being amortized over the period to the earliest put option date of the holders using the effective interest method.

[4] With the adoption of the accounting guidance on convertible debt securities in 2009, the effective interest rates for the 2026 Notes and the 2028 Notes are 5.840% and 7.192%, respectively.