Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Basic and Diluted Earnings:
Net earnings attributable to NNN		$ 290,113,000	$ 228,799,000	$ 299,180,000
Less: Excess of redemption value over carrying value of preferred shares redeemed		(10,897,000)	0	(9,856,000)
Net earnings attributable to common stockholders		264,217,000	210,859,000	258,183,000
Less: Earnings allocated to unvested restricted shares		(689,000)	(698,000)	(601,000)
Net earnings used in basic and diluted earnings per share		$ 263,528,000	$ 210,161,000	$ 257,582,000
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)		175,554,961	172,994,337	165,499,707
Less: Unvested restricted shares (in shares)		(328,070)	(337,078)	(295,773)
Less: Unvested contingent restricted shares (in shares)		(515,970)	(547,546)	(515,436)
Weighted Average Number of Shares Outstanding, Basic, Total		174,710,921	172,109,713	164,688,498
Other dilutive securities (shares)		107,978	107,364	395,181
Weighted average number of shares outstanding used in diluted earnings per share (in shares)		174,818,899	172,217,077	165,083,679
Series E Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends		$ 0	$ 0	$ (13,201,000)
Series F Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends		$ (14,999,000)	$ (17,940,000)	$ (17,940,000)
Less: Excess of redemption value over carrying value of preferred shares redeemed	$ (10,897,000)