Noncontrolling Interests - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 31, 2019 USD ($) shares	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2016 entity property
Noncontrolling interests
Conversion ratio		1
Number of properties acquired | property				2
Number of joint ventures controlling interest acquired | entity				2
Redemption of partnership units		$ 20,225	$ 0
Term Loans | $70 million senior unsecured term loan
Noncontrolling interests
Repayments of long-term debt	$ 70,000
Tau Operating Partnership
Noncontrolling interests
Number of partnership units redeemed | shares	317,022
Ownership interest (as a percent)	100.00%
Third-party partnership ownership interest (as a percent)	0.11%
Redemption of partnership units	$ 20,200
Excess of redemption of units over carrying value as reduction to common stock and paid in capital	$ 6,900
Realty Income, L.P.
Noncontrolling interests
Ownership interest (as a percent)		98.10%
Third-party partnership ownership interest (as a percent)		1.90%
Other Noncontrolling Interest Entity One
Noncontrolling interests
Ownership interest (as a percent)		95.00%