Organization and Summary of Significant Accounting Policies (Summary of NNN's Investment Portfolio) (Details) ft² in Thousands	3 Months Ended
	Mar. 31, 2019 ft² state property
Property Portfolio:
Total properties | property	2,984
Gross leasable area (square feet) | ft²	30,698
States | state	48
Weighted average remaining lease term (years)	11 years 4 months 24 days