Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 82,032	$ 61,120	$ 255,886	$ 192,805
Net earnings attributable to common stockholders	73,450	52,538	230,140	153,606
Less: Earnings allocated to unvested restricted shares	(147)	(132)	(412)	(399)
Net earnings used in basic and diluted earnings per share	$ 73,303	$ 52,406	$ 229,728	$ 153,207
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	157,634,757	150,076,348	155,316,866	148,934,825
Less: Unvested restricted stock (in shares)	(294,453)	(277,713)	(276,046)	(288,238)
Less: Unvested contingent restricted shares (in shares)	(487,320)	(457,610)	(458,371)	(423,353)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	156,852,984	149,341,025	154,582,449	148,223,234
Other dilutive securities (in shares)	433,181	326,584	425,408	303,127
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	157,286,165	149,667,609	155,007,857	148,526,361
Series D Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ 0	$ 0	$ 0	$ (3,598)
Excess of redemption value over carrying value of Series D preferred shares redeemed	0	0	0	(9,855)
Series E Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	(4,097)	(4,097)	(12,291)	(12,291)
Series F Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ (4,485)	$ (4,485)	$ (13,455)	$ (13,455)