Equity - Basic and Diluted Earnings Per Share (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Net Income Attributable to W. P. Carey	$ 193,263	$ 77,348	$ 75,681	$ 65,274	$ 75,209	$ 80,278	$ 64,318	$ 57,484	$ 411,566	$ 277,289	$ 267,747
Net income attributable to nonvested participating RSUs and RSAs									(340)	(784)	(886)
Net income – basic and diluted									$ 411,226	$ 276,505	$ 266,861
Weighted-average shares outstanding – basic (shares)									117,494,969	107,824,738	106,743,012
Effect of dilutive securities (shares)									211,476	211,233	330,191
Weighted-average shares outstanding – diluted (shares)									117,706,445	108,035,971	107,073,203
Anti-dilutive shares									0	0	0