Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended
		Oct. 11, 2016	Oct. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Feb. 28, 2015
Class of Stock [Line Items]
Total allowable shares (in shares)				375,000,000		375,000,000		375,000,000
Net proceeds						$ 277,076	$ 127,485
Total shares issued (in shares)				147,123,246		147,123,246		141,007,725
Stock issuance costs						$ 4,266	2,206
Common stock dividends				$ 66,676	$ 58,274	$ 190,277	$ 169,674
Common stock per share (in dollars per share)				$ 0.455	$ 0.435	$ 1.325	$ 1.275
Subsequent Event
Class of Stock [Line Items]
Stock issuance costs		$ 10,722
Common stock, dividends, per share, declared (in dollars per share)			$ 0.455
Series D Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends	[1]			$ 4,762	$ 4,762	$ 14,285	$ 14,285
Preferred stock per share (in dollars per share)	[1]			$ 0.414063	$ 0.414063	$ 1.242188	$ 1.242188
Series E Preferred Stock
Class of Stock [Line Items]
Preferred stock dividends	[1]			$ 4,097	$ 4,097	$ 12,291	$ 12,291
Preferred stock per share (in dollars per share)	[1]			$ 0.356250	$ 0.356250	$ 1.068750	$ 1.068750
DRIP
Class of Stock [Line Items]
Total allowable shares (in shares)									16,000,000
Shares of common stock (in shares)						164,640	147,614
Net proceeds						$ 7,376	$ 5,409
2016 ATM
Class of Stock [Line Items]
Total allowable shares (in shares)				12,000,000		12,000,000
Total shares issued (in shares)				4,223,290		4,223,290
Shares of common stock (in shares)						5,716,222
Average price per share (net) (in dollars per share)						$ 46.48
Net proceeds						$ 265,696
Stock issuance costs	[2]					$ 4,266
2015 ATM
Class of Stock [Line Items]
Total allowable shares (in shares)				10,000,000		10,000,000
Total shares issued (in shares)				9,852,465		9,852,465
Shares of common stock (in shares)							3,105,502
Average price per share (net) (in dollars per share)							$ 38.71
Net proceeds							$ 120,199
Stock issuance costs	[2]						$ 2,024
2013 ATM
Class of Stock [Line Items]
Total allowable shares (in shares)				9,000,000		9,000,000
Total shares issued (in shares)				6,252,812		6,252,812

[1] The Series D and E preferred stock have no maturity date and will remain outstanding unless redeemed by NNN. The earliest redemption date for the Series D and Series E preferred stock is February 2017 and May 2018, respectively.

[2] Stock issuance costs consist primarily of underwriters' fees and commissions, and legal and accounting fees.