Organization and Summary of Significant Accounting Policies (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Basic and Diluted Earnings:
Net earnings attributable to NNN	$ 42,471	$ 55,198	$ 46,188	$ 53,978	$ 53,757	$ 47,940	$ 45,571	$ 43,333	$ 197,836	$ 190,601	$ 160,145
Net earnings attributable to common stockholders									162,402	155,167	132,222
Less: Earnings attributable to unvested restricted shares									(706)	(773)	(718)
Net earnings used in basic and diluted earnings per share									$ 161,696	$ 154,394	$ 131,504
Basic and Diluted Weighted Average Shares Outstanding:
Weighted average number of shares outstanding (in shares)									134,868,640	125,221,358	118,969,771
Less: Unvested restricted shares (in shares)									(412,505)	(467,968)	(448,590)
Less: Unvested contingent shares (in shares)									(457,461)	(495,832)	(317,033)
Weighted average number of shares outstanding used in basic earnings per share (in shares)									133,998,674	124,257,558	118,204,148
Convertible debt (shares)									0	0	1,468,559
Other (shares)									490,742	452,668	192,117
Weighted average number of shares outstanding used in diluted earnings per share (shares)									134,489,416	124,710,226	119,864,824
Series D Preferred Stock
Basic and Diluted Earnings:
Preferred stock dividends									$ (19,047)	$ (19,047)	$ (19,047)
Series E Preferred Stock
Basic and Diluted Earnings:
Preferred stock dividends									$ (16,387)	$ (16,387)	$ (8,876)