Mortgages Payable (Details) (USD $)	Dec. 31, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
Outstanding Principal Balance	$ 10,602,000		$ 23,171,000
Mortgages [Member]
Debt Instrument [Line Items]
Carrying Value of Encumbered Assets	23,830,000	[1]
Outstanding Principal Balance	10,602,000	[1]	23,171,000	[1]
Long-term Debt, Fiscal Year Maturity [Abstract]
2013	1,127,000
2014	1,158,000
2015	1,207,000
2016	6,842,000
2017	146,000
Thereafter	122,000
December 2001 - $623 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	623,000	[2]
Interest Rate	9.00%	[2]
Carrying Value of Encumbered Assets	543,000	[1],[2]
Outstanding Principal Balance	95,000	[2]	158,000	[2]
December 2001 - $698 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	698,000	[2]
Interest Rate	9.00%	[2]
Carrying Value of Encumbered Assets	1,047,000	[1],[2]
Outstanding Principal Balance	299,000	[2]	333,000	[2]
December 2001 - $485 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	485,000	[2]
Interest Rate	9.00%	[2]
Carrying Value of Encumbered Assets	1,013,000	[1],[2]
Outstanding Principal Balance	155,000	[2]	172,000	[2]
June 2002 - $21,000 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	21,000,000
Interest Rate	6.90%
Carrying Value of Encumbered Assets	0	[1]
Outstanding Principal Balance	0		18,488,000
February 2004 - $6,952 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	6,952,000	[2]
Interest Rate	6.90%	[2]
Carrying Value of Encumbered Assets	11,039,000	[1],[2]
Outstanding Principal Balance	2,892,000	[2]	3,485,000	[2]
March 2005 - $1,015 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	1,015,000	[2]
Interest Rate	8.14%	[2]
Carrying Value of Encumbered Assets	1,283,000	[1],[2]
Outstanding Principal Balance	439,000	[2]	535,000	[2]
Mortgage Payable, Issued June 2012 [Member] | Mortgages [Member]
Debt Instrument [Line Items]
Initial Balance	6,850,000	[2],[3]
Interest Rate	5.75%	[2],[3]
Carrying Value of Encumbered Assets	8,905,000	[1],[2],[3]
Outstanding Principal Balance	$ 6,722,000	[2],[3]	$ 0	[2],[3]

[1] Each loan is secured by a first mortgage lien on certain of NNN’s properties. The carrying values of the assets are as of December 31, 2012.

[2] Date entered represents the date that NNN acquired real estate subject to a mortgage securing a loan. The corresponding original principal balance represents the outstanding principal balance at the time of acquisition.

[3] Initial balance and outstanding principal balance includes unamortized premium.