Quarterly Financial Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Revenues	$ 103,648		$ 89,059		$ 100,482		$ 96,015		$ 92,183		$ 84,250		$ 81,096		$ 77,132		$ 392,327	$ 331,536	$ 258,690
Net earnings attributable to NNN	44,241		40,663		44,352		37,486		34,066		38,015		33,505		29,832		160,145	142,015	92,325
Basic (in dollars per share)	$ 0.29	[1]	$ 0.33	[1]	$ 0.29	[1]	$ 0.28	[1]	$ 0.26	[1]	$ 0.31	[1]	$ 0.26	[1]	$ 0.23	[1]	$ 1.11	$ 1.13	$ 0.96
Diluted (in dollars per share)	$ 0.29	[1]	$ 0.32	[1]	$ 0.29	[1]	$ 0.27	[1]	$ 0.25	[1]	$ 0.30	[1]	$ 0.26	[1]	$ 0.23	[1]	$ 1.10	$ 1.11	$ 0.96
Revenues as originally reported
Segment Reporting Information [Line Items]
Revenues	103,648		88,899		100,621		96,121		92,565		85,013		82,751		78,658
Reclassified to discontinued operations
Segment Reporting Information [Line Items]
Revenues	$ 0		$ 160		$ (139)		$ (106)		$ (382)		$ (763)		$ (1,655)		$ (1,526)

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