Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues as originally reported																	$ 533,647	$ 482,916	$ 434,877
Net earnings attributable to NNN’s stockholders	$ 66,092		$ 50,784		$ 51,942		$ 70,683		$ 42,471		$ 55,198		$ 46,188		$ 53,978		$ 239,500	$ 197,836	$ 190,601
Net earnings per share:
Basic (in dollars per share)	$ 0.37	[1]	$ 0.29	[1]	$ 0.30	[1]	$ 0.44	[1]	$ 0.24	[1]	$ 0.34	[1]	$ 0.28	[1]	$ 0.34	[1]	$ 1.39	$ 1.21	$ 1.24
Diluted (in dollars per share)	$ 0.37	[1]	$ 0.28	[1]	$ 0.30	[1]	$ 0.44	[1]	$ 0.24	[1]	$ 0.34	[1]	$ 0.28	[1]	$ 0.34	[1]	$ 1.38	$ 1.20	$ 1.24
Revenues as originally reported
Segment Reporting Information [Line Items]
Revenues as originally reported	$ 141,261		$ 134,558		$ 130,998		$ 126,999		$ 126,377		$ 123,143		$ 117,208		$ 116,187

[1] Calculated independently for each period and consequently, the sum of the quarters may differ from the annual amount.