Organization and Summary of Significant Accounting Policies (Summary of NNN's Investment Portfolio) (Details) ft² in Thousands	6 Months Ended
	Jun. 30, 2021 ft² state property
Property Portfolio:
Total properties | property	3,173
Gross leasable area (square feet) | ft²	32,664
States | state	48
Weighted average remaining lease term	10 years 7 months 6 days