Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 82,933	$ 56,069	$ 212,543	$ 167,512
Less: preferred stock dividends	(4,485)	(4,485)	(13,455)	(13,455)
Net earnings attributable to common stockholders	78,448	51,584	199,088	154,057
Less: Earnings allocated to unvested restricted shares	(180)	(179)	(509)	(516)
Net earnings used in basic and diluted earnings per share	$ 78,268	$ 51,405	$ 198,579	$ 153,541
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	175,607,905	173,596,374	175,530,702	172,579,042
Less: Unvested restricted shares (in shares)	(340,725)	(344,429)	(323,808)	(332,730)
Less: Unvested contingent restricted shares (in shares)	(637,738)	(570,809)	(596,868)	(539,735)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	174,629,442	172,681,136	174,610,026	171,706,577
Other dilutive securities (in shares)	109,461	101,130	106,027	108,800
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	174,738,903	172,782,266	174,716,053	171,815,377