Real Estate (Impairments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Real Estate [Abstract]
Continuing operations	$ 89	$ 249	$ 485	$ 3,100
Discontinued operations	0	904	63	904
Impairment Losses and Other Charges	$ 89	$ 1,153	$ 548	$ 4,004

Impairment Losses, Continuing Operations, Net of Recoveries

No definition available.

Name:	nnn_ImpairmentLossesContinuingOperationsNetofRecoveries
Namespace Prefix:	nnn_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration