Organization and Summary of Significant Accounting Policies (Summary of NNN's Investment Portfolio) (Details) ft² in Thousands	3 Months Ended
	Mar. 31, 2021 ft² property state
Property Portfolio:
Total properties | property	3,161
Gross leasable area (square feet) | ft²	32,717
States | state	48
Weighted average remaining lease term	10 years 7 months 6 days