Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings per Share) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 103,280	$ 73,657
Net earnings attributable to common stockholders	94,698	51,622
Less: Earnings allocated to unvested restricted shares	(147)	(130)
Net earnings used in basic and diluted earnings per share	$ 94,551	$ 51,492
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)	153,678,913	147,581,522
Less: Unvested restricted stock (in shares)	(237,617)	(285,887)
Less: Unvested contingent restricted shares (in shares)	(400,240)	(365,957)
Weighted average number of shares outstanding used in basic earnings per share (in shares)	153,041,056	146,929,678
Other dilutive securities (in shares)	352,327	349,859
Weighted average number of shares outstanding used in diluted earnings per share (in shares)	153,393,383	147,279,537
Series D Preferred Stock
Basic and Diluted Earnings:
Less: preferred stock dividends	$ 0	$ (3,598)
Excess of redemption value over carrying value of Series D preferred shares redeemed	0	(9,855)
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)