Organization and Summary of Significant Accounting Policies (Computation Of Basic And Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Net earnings attributable to NNN	$ 40,663,000	$ 38,015,000	$ 33,505,000	$ 29,832,000	$ 27,570,000	$ 22,632,000	$ 21,303,000	$ 20,820,000	$ 142,015,000		$ 92,325,000		$ 72,997,000
Less: Preferred stock dividends											(6,785,000)		(6,785,000)
Less: Excess of redemption value over carrying value of preferred shares redeemed									(3,098,000)		0		0
Net earnings attributable to common stockholders									121,489,000		85,540,000		66,212,000
Less: Earnings attributable to unvested restricted shares									(741,000)		(622,000)		(299,000)
Net earnings used in basic earnings per share									120,748,000		84,918,000		65,913,000
Reallocated undistributed income (loss)									(5,000)		(2,000)		0
Net earnings used in diluted earnings per share									120,743,000		84,916,000		65,913,000
Weighted average number of shares outstanding									107,873,577		88,972,723		83,320,921
Less: Unvested restricted stock (in shares)									(654,127)		(630,102)		(605,276)
Less: Contingent shares (in shares)									254,294		242,545		0
Weighted average number of shares outstanding used in basic earnings per share									106,965,156		88,100,076		82,715,645
Contingent shares (in shares)									6,333		66,001		0
Convertible debt (in shares)									1,987,842		512,024		0
Common stock options (in shares)									992		2,881		3,814
Directors' deferred fee plan (in shares)									157,192		156,075		129,903
Weighted average number of shares outstanding used in diluted earnings per share									109,117,515		88,837,057		82,849,362
Series C Depositary Share [Member]
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Less: Preferred stock dividends									(1,979,000)	[1]	(6,785,000)	[1]	(6,785,000)	[1]
Series D Depositary Share [Member]
Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Line Items]
Less: Preferred stock dividends									$ (15,449,000)	[2]	$ 0	[2]	$ 0	[2]

[1] The Series C Preferred Stock was redeemed in March 2012. The dividends paid during the quarter ended March 31, 2012 include accumulated and unpaid dividends through the redemption date.

[2] The Series D Preferred Stock dividends paid during the quarter ended June 30, 2012 include accumulated and unpaid dividends from the issuance date through the declaration date. The Series D Preferred Stock has no maturity date and will remain outstanding unless redeemed.