Organization and Summary of Significant Accounting Policies (Summary of NNN's Investment Portfolio) (Details) ft² in Thousands	9 Months Ended
	Sep. 30, 2017 ft² state property
Accounting Policies [Abstract]
Total properties | property	2,687
Gross leasable area (square feet) | ft²	28,250
States | state	48
Weighted average remaining lease term (years)	11 years 4 months 24 days