Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 73,023	$ 46,265	$ 129,610	$ 111,443
Less: preferred stock dividends	(4,485)	(4,485)	(8,970)	(8,970)
Net earnings attributable to common stockholders	68,538	41,780	120,640	102,473
Less: Earnings allocated to unvested restricted shares	(178)	(176)	(328)	(336)
Net earnings used in basic and diluted earnings per share	$ 68,360	$ 41,604	$ 120,312	$ 102,137
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	175,590,102	172,301,757	175,491,461	172,064,786
Less: Unvested restricted shares (in shares)	(341,467)	(342,079)	(315,209)	(326,816)
Less: Unvested contingent restricted shares (in shares)	(637,738)	(570,809)	(576,094)	(524,027)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	174,610,897	171,388,869	174,600,158	171,213,943
Other dilutive securities (in shares)	115,915	96,416	132,918	159,873
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	174,726,812	171,485,285	174,733,076	171,373,816