Employee Benefit Plan	12 Months Ended
	Dec. 31, 2020
Retirement Benefits [Abstract]
Employee Benefit Plan	Employee Benefit Plan:Effective January 1, 1998, NNN adopted a defined contribution retirement plan (the “Retirement Plan”) covering substantially all of the employees of NNN. The Retirement Plan permits participants to defer a portion of their compensation, as defined in the Retirement Plan, subject to limits established by the Code. NNN generally matches 60 percent of the first eight percent of a participant’s contributions. Additionally, NNN may make discretionary contributions. NNN’s contributions to the Retirement Plan for the years ended December 31, 2020, 2019 and 2018 totaled $546,000, $541,000 and $516,000, respectively.