Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 80,023	$ 103,280
Net earnings attributable to common stockholders	71,441	94,698
Less: Earnings allocated to unvested restricted shares	(116)	(147)
Net earnings used in basic and diluted earnings per share	$ 71,325	$ 94,551
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	161,785,877	153,678,913
Less: Unvested restricted stock (in shares)	(232,795)	(237,617)
Less: Unvested contingent restricted shares (in shares)	(447,767)	(400,240)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	161,105,315	153,041,056
Other dilutive securities (in shares)	508,759	352,327
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	161,614,074	153,393,383
Series E Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ (4,097)	$ (4,097)
Series F Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ (4,485)	$ (4,485)