CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Rental income from operating leases	$ 565,405,000	$ 512,883,000	$ 462,346,000
Earned income from direct financing leases	978,000	1,336,000	1,506,000
Percentage rent	1,700,000	1,735,000	1,430,000
Real estate expense reimbursement from tenants	15,512,000	14,984,000	14,868,000
Interest and other income from real estate transactions	724,000	1,032,000	988,000
Interest income on commercial mortgage residual interests	614,000	1,677,000	1,778,000
Total revenues	584,933,000	533,647,000	482,916,000
Operating expenses:
General and administrative	33,805,000	36,508,000	34,736,000
Real estate	23,105,000	20,852,000	19,776,000
Depreciation and amortization	173,720,000	149,101,000	134,798,000
Impairment – commercial mortgage residual interests valuation	0	6,830,000	531,000
Impairment losses – real estate and other charges, net of recoveries	8,955,000	11,287,000	4,420,000
Retirement severance costs	7,845,000	0	0
Total operating expenses	247,430,000	224,578,000	194,261,000
Earnings from operations	337,503,000	309,069,000	288,655,000
Other expenses (revenues):
Interest and other income	(322,000)	(170,000)	(109,000)
Interest expense	109,109,000	96,352,000	90,008,000
Real estate acquisition costs	0	563,000	927,000
Total other expenses (revenues)	108,787,000	96,745,000	90,826,000
Earnings from operations before income tax expense	228,716,000	212,324,000	197,829,000
Income tax expense	0	0	(10,318,000)
Earnings before gain on disposition of real estate, net of income tax expense	228,716,000	212,324,000	187,511,000
Gain on disposition of real estate, net of income tax expense	36,655,000	27,182,000	10,450,000
Net earnings	265,371,000	239,506,000	197,961,000
Earnings attributable to noncontrolling interests	(398,000)	(6,000)	(125,000)
Net earnings attributable to NNN	264,973,000	239,500,000	197,836,000
Net earnings attributable to common stockholders	$ 217,193,000	$ 200,877,000	$ 162,402,000
Net earnings per share of common stock:
Basic (in dollars per share)	$ 1.45	$ 1.39	$ 1.21
Diluted (in dollars per share)	$ 1.45	$ 1.38	$ 1.20
Weighted average number of common shares outstanding:
Basic (in shares)	149,111,188	144,176,224	133,998,674
Diluted (in shares)	149,432,641	144,660,633	134,489,416
Other comprehensive income:
Net earnings attributable to NNN	$ 264,973,000	$ 239,500,000	$ 197,836,000
Amortization of deferred interest rate hedges	1,932,000	2,802,000	1,902,000
Deferred fair value of forward starting swaps	(7,688,000)	13,345,000	(13,369,000)
Net loss – commercial mortgage residual interests	0	(4,454,000)	(339,000)
Net gain – available-for-sale securities	209,000	468,000	112,000
Comprehensive income attributable to NNN	259,426,000	251,661,000	186,142,000
Series D Preferred Stock
Other expenses (revenues):
Preferred stock dividends	(3,598,000)	(19,047,000)	(19,047,000)
Excess of redemption value over carrying value of Series D preferred shares redeemed	(9,855,000)	0	0
Series E Preferred Stock
Other expenses (revenues):
Preferred stock dividends	(16,387,000)	(16,387,000)	(16,387,000)
Series F Preferred Stock
Other expenses (revenues):
Preferred stock dividends	$ (17,940,000)	$ (3,189,000)	$ 0