Organization and Summary of Significant Accounting Policies (Summary of NNN's Investment Portfolio) (Details) ft² in Thousands	9 Months Ended
	Sep. 30, 2019 ft² state property
Property Portfolio:
Total properties | property	3,057
Gross leasable area (square feet) | ft²	32,209
States | state	48
Weighted average remaining lease term (years)	11 years 2 months 12 days