Real Estate (Commitments) (Details) $ in Thousands	Dec. 31, 2020 USD ($) property
Real Estate [Abstract]
Number of properties \| property	5
Total commitment	$ 42,443
Less amount funded	35,094
Remaining commitment	$ 7,349

Real Estate Investment, Funding Commitments, Remaining Commitment

No definition available.

Name:	nnn_RealEstateInvestmentFundingCommitmentsRemainingCommitment
Namespace Prefix:	nnn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant