Noncontrolling Interests (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($)	Dec. 31, 2016 entity property	Apr. 30, 2018 shares	Mar. 30, 2018 shares	Dec. 31, 2017 shares	Jun. 27, 2013 shares	Jan. 22, 2013 shares
Noncontrolling interests
Conversion ratio			1
Number of properties acquired | property					2
Number of joint ventures controlling interest acquired | entity					2
Change in the carrying value of all noncontrolling interests
Carrying value at beginning of the period			$ 19,207
Reallocation of equity			492
Redemptions			(2,829)
Shares issued in conjunction with acquisition			18,848
Distributions			(1,457)
Allocation of net income	$ 284	$ 133	753	$ 420
Carrying value at end of the period	$ 35,014		$ 35,014
Joint Venture One
Noncontrolling interests
Ownership interest (as a percent)	95.00%		95.00%
Joint Venture Two
Noncontrolling interests
Ownership interest (as a percent)	74.00%		74.00%
Other Noncontrolling Interests
Change in the carrying value of all noncontrolling interests
Carrying value at beginning of the period			$ 3,725
Reallocation of equity			(37)
Redemptions			0
Shares issued in conjunction with acquisition			0
Distributions			(235)
Allocation of net income			55
Carrying value at end of the period	$ 3,508		$ 3,508
Tau Operating Partnership
Noncontrolling interests
Realty Income partnership units, ownership interest (as a percent)	99.40%		99.40%
Change in the carrying value of all noncontrolling interests
Carrying value at beginning of the period			$ 13,322
Reallocation of equity			572
Redemptions			0
Shares issued in conjunction with acquisition			0
Distributions			(627)
Allocation of net income			250
Carrying value at end of the period	$ 13,517		$ 13,517
Number of partnership units outstanding | shares	317,022		317,022					317,022
Number of partnership units issued | shares										317,022
Realty Income, L.P.
Noncontrolling interests
Realty Income partnership units, ownership interest (as a percent)	98.50%		98.50%
Third party partnership units, ownership interest (as a percent)	1.50%		1.50%
Change in the carrying value of all noncontrolling interests
Carrying value at beginning of the period			$ 2,160
Reallocation of equity			(43)
Redemptions			(2,829)
Shares issued in conjunction with acquisition			18,848
Distributions			(595)
Allocation of net income			448
Carrying value at end of the period	$ 17,989		$ 17,989
Number of partnership units outstanding | shares	373,797		373,797					88,182
Number of partnership units issued | shares	373,797		373,797			131,790	242,007		534,546