Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 65,178	$ 80,023
Net earnings attributable to common stockholders	60,693	71,441
Less: Earnings allocated to unvested restricted shares	(160)	(116)
Net earnings used in basic and diluted earnings per share	$ 60,533	$ 71,325
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	171,827,815	161,785,877
Less: Unvested restricted stock (in shares)	(311,553)	(232,795)
Less: Unvested contingent restricted shares (in shares)	(477,245)	(447,767)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	171,039,017	161,105,315
Other dilutive securities (in shares)	192,811	508,759
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	171,231,828	161,614,074
Series E Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ 0	$ (4,097)
Series F Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ (4,485)	$ (4,485)