Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Financial Instruments, Owned, at Fair Value [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments:NNN believes the carrying value of its Credit Facility approximates fair value based upon its nature, terms and variable interest rate. NNN believes that the carrying value of its mortgages payable at December 31, 2020 and 2019, approximate fair value based upon current market prices of comparable instruments (Level 3). At December 31, 2020 and 2019, the fair value of NNN’s notes payable net of unamortized discount and excluding debt costs, was $3,532,908,000 and $3,074,538,000, respectively, based upon quoted market prices, which is a Level 1 valuation since NNN's notes payable are publicly traded.