Mortgages Payable (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Outstanding Principal Balance	$ 26,339,000		$ 9,475,000
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	26,339,000		9,475,000
Mortgages
Debt Instrument [Line Items]
Carrying Value of Encumbered Asset(s)	48,210,000	[1]
Outstanding Principal Balance	26,339,000		9,475,000
Long-term Debt, Fiscal Year Maturity [Abstract]
2015	1,870,000
2016	7,514,000
2017	3,441,000
2018	710,000
2019	688,000
Thereafter	12,116,000
Total	26,339,000		9,475,000
December 2001 - $623 | Mortgages
Debt Instrument [Line Items]
Initial Balance	623,000	[2],[3]
Interest Rate	9.00%	[2],[3]
Carrying Value of Encumbered Asset(s)	0	[1],[2],[3]
Outstanding Principal Balance	0	[2],[3]	27,000	[2],[3]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	0	[2],[3]	27,000	[2],[3]
December 2001 - $698 | Mortgages
Debt Instrument [Line Items]
Initial Balance	698,000	[2],[3]
Interest Rate	9.00%	[2],[3]
Carrying Value of Encumbered Asset(s)	868,000	[1],[2],[3]
Outstanding Principal Balance	223,000	[2],[3]	263,000	[2],[3]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	223,000	[2],[3]	263,000	[2],[3]
December 2001 - $485 | Mortgages
Debt Instrument [Line Items]
Initial Balance	485,000	[2],[3]
Interest Rate	9.00%	[2],[3]
Carrying Value of Encumbered Asset(s)	841,000	[1],[2],[3]
Outstanding Principal Balance	116,000	[2],[3]	136,000	[2],[3]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	116,000	[2],[3]	136,000	[2],[3]
February 2004 | Mortgages
Debt Instrument [Line Items]
Initial Balance	6,952,000	[2],[3]
Interest Rate	6.90%	[2],[3]
Carrying Value of Encumbered Asset(s)	10,554,000	[1],[2],[3]
Outstanding Principal Balance	1,577,000	[2],[3]	2,257,000	[2],[3]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	1,577,000	[2],[3]	2,257,000	[2],[3]
March 2005 | Mortgages
Debt Instrument [Line Items]
Initial Balance	1,015,000	[2],[3]
Interest Rate	8.14%	[2],[3]
Carrying Value of Encumbered Asset(s)	1,245,000	[1],[2],[3]
Outstanding Principal Balance	222,000	[2],[3]	335,000	[2],[3]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	222,000	[2],[3]	335,000	[2],[3]
June 2012 | Mortgages
Debt Instrument [Line Items]
Initial Balance	6,850,000	[2],[3],[4]
Interest Rate	5.75%	[2],[3],[4]
Carrying Value of Encumbered Asset(s)	8,529,000	[1],[2],[3],[4]
Outstanding Principal Balance	6,180,000	[2],[3],[4]	6,457,000	[2],[3],[4]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	6,180,000	[2],[3],[4]	6,457,000	[2],[3],[4]
September 2014 | Mortgages
Debt Instrument [Line Items]
Initial Balance	2,957,000	[2],[3],[4]
Interest Rate	6.40%	[2],[3],[4]
Carrying Value of Encumbered Asset(s)	3,797,000	[1],[2],[3],[4]
Outstanding Principal Balance	2,922,000	[2],[3],[4]	0	[2],[3],[4]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	2,922,000	[2],[3],[4]	0	[2],[3],[4]
November 2014 | Mortgages
Debt Instrument [Line Items]
Initial Balance	15,151,000	[2],[3],[4]
Interest Rate	5.23%	[2],[3],[4]
Carrying Value of Encumbered Asset(s)	22,376,000	[1],[2],[3],[4]
Outstanding Principal Balance	15,099,000	[2],[3],[4]	0	[2],[3],[4]
Long-term Debt, Fiscal Year Maturity [Abstract]
Total	$ 15,099,000	[2],[3],[4]	$ 0	[2],[3],[4]

[1] Each loan is secured by a first mortgage lien on certain of the Properties. The carrying values of the assets are as of December 31, 2014

[2] Monthly payments include interest and principal, if any; the balance is due at maturity.

[3] Date entered represents the date that NNN acquired real estate subject to a mortgage securing a loan.

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