Notes Payable (Details)		12 Months Ended
		Dec. 31, 2016 USD ($) instrument derivative	Dec. 31, 2015 USD ($)	Oct. 31, 2015 USD ($) derivative	May 31, 2014 USD ($) derivative	Apr. 30, 2013 USD ($) derivative	Jul. 31, 2011 USD ($) derivative	Sep. 30, 2007 USD ($)
Notes Payable [Line Items]
Number of derivative financial instruments outstanding | instrument		0
Debt issuance costs incurred		$ 21,157,000
2017 Notes
Notes Payable [Line Items]
Principal	[1]	250,000,000
Discount	[1],[2]	877,000
Net Price	[1]	$ 249,123,000
Stated Rate	[1]	6.875%
Effective Rate	[1],[3]	6.924%
2017 Notes | Interest Rate Swap
Notes Payable [Line Items]
Notional amount								$ 100,000,000
Liability amount from termination of hedge agreement								3,260,000
Liability amount from termination of hedge agreement, comprehensive income								$ 3,228,000
2021 Notes
Notes Payable [Line Items]
Principal	[4]	$ 300,000,000
Discount	[2],[4]	4,269,000
Net Price	[4]	$ 295,731,000
Stated Rate	[4]	5.50%
Effective Rate	[3],[4]	5.689%
2021 Notes | Interest Rate Swap
Notes Payable [Line Items]
Notional amount							$ 150,000,000
Liability amount from termination of hedge agreement							5,300,000
Liability amount from termination of hedge agreement, comprehensive income							$ 5,218,000
Number of derivative financial instruments outstanding | derivative							2
2022 Notes
Notes Payable [Line Items]
Principal		$ 325,000,000
Discount	[2]	4,989,000
Net Price		$ 320,011,000
Stated Rate		3.80%
Effective Rate	[3]	3.985%
2023 Notes
Notes Payable [Line Items]
Principal	[5]	$ 350,000,000
Discount	[2],[5]	2,594,000
Net Price	[5]	$ 347,406,000
Stated Rate	[5]	3.30%
Effective Rate	[3],[5]	3.388%
2023 Notes | Forward Starting Swaps
Notes Payable [Line Items]
Notional amount						$ 240,000,000
Liability amount from termination of hedge agreement						3,156,000
Liability amount from termination of hedge agreement, comprehensive income						$ 3,141,000
Number of derivative financial instruments outstanding | derivative						4
2024 Notes
Notes Payable [Line Items]
Principal	[6]	$ 350,000,000
Discount	[2],[6]	707,000
Net Price	[6]	$ 349,293,000
Stated Rate	[6]	3.90%
Effective Rate	[3],[6]	3.924%
2024 Notes | Forward Starting Swaps
Notes Payable [Line Items]
Notional amount					$ 225,000,000
Liability amount from termination of hedge agreement					$ 6,312,000
Number of derivative financial instruments outstanding | derivative					3
2025 Notes
Notes Payable [Line Items]
Principal	[7]	$ 400,000,000
Discount	[2],[7]	964,000
Net Price	[7]	$ 399,036,000
Stated Rate	[7]	4.00%
Effective Rate	[3],[7]	4.029%
2025 Notes | Forward Starting Swaps
Notes Payable [Line Items]
Notional amount				$ 300,000
Liability amount from termination of hedge agreement				$ 13,369,000
Number of derivative financial instruments outstanding | derivative				4
2025 Notes
Notes Payable [Line Items]
Principal	[8]	$ 350,000,000
Discount	[2],[8]	3,860,000
Net Price	[8]	$ 346,140,000
Stated Rate	[8]	3.60%
Effective Rate	[3],[8]	3.733%
2025 Notes | Forward Starting Swaps
Notes Payable [Line Items]
Notional amount		$ 180,000,000
Liability amount from termination of hedge agreement		$ 13,345,000
Number of derivative financial instruments outstanding | derivative		2
2015 Notes
Notes Payable [Line Items]
Principal			$ 150,000,000
Stated Rate			6.15%

[1] NNN entered into an interest rate hedge with a notional amount of $100,000. Upon issuance of the 2017 Notes, NNN terminated the interest rate hedge agreement resulting in a liability of $3,260, of which $3,228 was recorded to other comprehensive income. The liability has been deferred and is being amortized as an adjustment to interest expense over the term of the notes using the effective interest method.

[2] The note discounts are amortized to interest expense over the respective term of each debt obligation using the effective interest method.

[3] Includes the effects of the discount at issuance

[4] NNN entered into two interest rate hedges with a total notional amount of $150,000. Upon issuance of the 2021 Notes, NNN terminated the interest rate hedge agreements resulting in a liability of $5,300, of which $5,218 was deferred in other comprehensive income. The deferred liability is being amortized over the term of the notes using the effective interest method.

[5] NNN entered into four forward starting swaps with an aggregate notional amount of $240,000. Upon issuance of the 2023 Notes, NNN terminated the forward starting swaps resulting in a liability of $3,156, of which $3,141 was deferred in other comprehensive income. The deferred liability is being amortized over the term of the notes using the effective interest method.

[6] NNN entered into three forward starting swaps with an aggregate notional amount of $225,000. Upon issuance of the 2024 Notes, NNN terminated the forward starting swaps resulting in a liability of $6,312, which was deferred in other comprehensive income. The deferred liability is being amortized over the term of the notes using the effective interest method.

[7] NNN entered into four forward starting swaps with an aggregate notional amount of $300,000. Upon issuance of the 2025 Notes, NNN terminated the forward starting swaps resulting in a liability of $13,369, which was deferred in other comprehensive income. The deferred liability is being amortized over the term of the notes using the effective interest method.

[8] NNN entered into two forward starting swaps with an aggregate notional amount of $180,000. Upon issuance of the 2026 Notes, NNN terminated the forward starting swaps resulting in a gain of $13,345, which was deferred in other comprehensive income. The deferred asset is being amortized over the term of the notes using the effective interest method.