Segment Information Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011 segments	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011 segments	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting Information [Line Items]
Number of Segments	1								1
External revenues									$ 261,128	$ 222,663	$ 221,470
Intersegment revenues									0	0	0
Interest Revenue, Operating									3,071	3,278	4,476
Interest revenue									3,071	3,278	4,476
Other Income									3,105	3,460	4,252
Gain on the disposition of real estate, Inventory Portfolio									297	641	37
Retail operations, net									2,043	1,311	419
Interest Expense									74,845	65,179	62,151
Depreciation and amortization									58,115	48,047	46,258
Other Expenses									45,701	35,998	35,271
Impairment losses and other charges, net of recoveries									(1,431)	7,458	36,080
Impairment - commercial mortgage residual interests valuation									1,024	3,995	498
Restructuring costs									0	0	731
Equity in earnings of unconsolidated affiliate									474	428	421
Gain on extinguishment of debt									0	0	3,432
Income Tax Expense (Benefit)									(779)	(475)	1,049
Earnings (loss) from continuing operations									91,085	70,629	54,567
Earnings from discontinued operations, net of income tax expense									1,331	2,724	1,832
Earnings (loss) including noncontrolling interests									92,416	73,353	56,399
Earnings attributable to noncontrolling interests from continuing operations									11	367	1,423
Loss attributable to noncontrolling interests from discontinued operations									80	(11)	166
Net earnings attributable to NNN	27,570	22,632	21,303	20,820	14,215	21,210	21,207	16,365	92,325	72,997	54,810
Assets	3,434,429				2,713,575				3,434,429	2,713,575	2,590,962
Additions to long-lived assets, Real estate									759,405	231,406	46,890
Investment Assets Member
Segment Reporting Information [Line Items]
External revenues									261,099	222,703	221,276
Intersegment revenues									50	671	3,035
Interest Revenue, Operating									2,992	3,230	4,446
Interest revenue									2,992	3,230	4,446
Other Income									3,105	3,460	4,252
Gain on the disposition of real estate, Inventory Portfolio									0	0	0
Retail operations, net									2,043	1,311	419
Interest Expense									76,223	67,834	66,018
Depreciation and amortization									58,110	48,039	46,248
Other Expenses									40,973	31,669	30,191
Impairment losses and other charges, net of recoveries									1,500	7,458	29,367
Impairment - commercial mortgage residual interests valuation									1,024	3,995	498
Restructuring costs											731
Equity in earnings of unconsolidated affiliate									722	(372)	(12,280)
Gain on extinguishment of debt											3,432
Income Tax Expense (Benefit)									(790)	(1,434)	462
Earnings (loss) from continuing operations									91,391	70,574	51,989
Earnings from discontinued operations, net of income tax expense									934	2,432	3,338
Earnings (loss) including noncontrolling interests									92,325	73,006	55,327
Earnings attributable to noncontrolling interests from continuing operations									0	9	517
Loss attributable to noncontrolling interests from discontinued operations									0	0	0
Net earnings attributable to NNN									92,325	72,997	54,810
Assets	3,560,485				2,846,036				3,560,485	2,846,036	2,588,408
Additions to long-lived assets, Real estate									758,380	230,928	44,433
Inventory Assets Member
Segment Reporting Information [Line Items]
External revenues									29	(40)	194
Intersegment revenues									0	534	1,042
Interest Revenue, Operating									79	48	30
Interest revenue									79	48	30
Other Income									0	0	0
Gain on the disposition of real estate, Inventory Portfolio									297	426	5
Retail operations, net									0	0	0
Interest Expense									(1,328)	(1,450)	188
Depreciation and amortization									5	8	10
Other Expenses									4,728	4,329	5,080
Impairment losses and other charges, net of recoveries									(2,931)	260	6,713
Impairment - commercial mortgage residual interests valuation									0	0	0
Restructuring costs											0
Equity in earnings of unconsolidated affiliate									0	0	0
Gain on extinguishment of debt											0
Income Tax Expense (Benefit)									11	959	587
Earnings (loss) from continuing operations									(58)	(1,220)	(10,133)
Earnings from discontinued operations, net of income tax expense									397	292	(1,506)
Earnings (loss) including noncontrolling interests									339	(928)	(11,639)
Earnings attributable to noncontrolling interests from continuing operations									11	358	906
Loss attributable to noncontrolling interests from discontinued operations									80	(11)	166
Net earnings attributable to NNN									248	(1,275)	(12,711)
Assets	35,375				38,997				35,375	38,997	237,715
Additions to long-lived assets, Real estate									1,025	478	2,457
Eliminations (Intercompany) Member
Segment Reporting Information [Line Items]
External revenues									0	0	0
Intersegment revenues									(50)	(1,205)	(4,077)
Interest Revenue, Operating									0	0	0
Interest revenue									0	0	0
Other Income									0	0	0
Gain on the disposition of real estate, Inventory Portfolio									0	215	32
Retail operations, net									0	0	0
Interest Expense									(50)	(1,205)	(4,055)
Depreciation and amortization									0	0	0
Other Expenses									0	0	0
Impairment losses and other charges, net of recoveries									0	(260)	0
Impairment - commercial mortgage residual interests valuation									0	0	0
Restructuring costs											0
Equity in earnings of unconsolidated affiliate									(248)	800	12,701
Gain on extinguishment of debt											0
Income Tax Expense (Benefit)									0	0	0
Earnings (loss) from continuing operations									(248)	1,275	12,711
Earnings from discontinued operations, net of income tax expense									0	0	0
Earnings (loss) including noncontrolling interests									(248)	1,275	12,711
Earnings attributable to noncontrolling interests from continuing operations									0	0	0
Loss attributable to noncontrolling interests from discontinued operations									0	0	0
Net earnings attributable to NNN									(248)	1,275	12,711
Assets	(161,431)				(171,458)				(161,431)	(171,458)	(235,161)
Additions to long-lived assets, Real estate									$ 0	$ 0	$ 0