Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Data
Revenues	$ 311,227	$ 318,005	$ 305,211	$ 298,323	$ 273,395	$ 209,384	$ 201,143	$ 201,810	$ 1,232,766	$ 885,732	$ 848,302
Expenses	175,816	198,409	179,170	177,722	185,346	110,937	109,202	120,966	731,117	526,451	489,748
Net income	129,792	41,835	66,121	68,796	195,278	81,573	79,424	68,066	306,544	424,341	285,083
Net income attributable to noncontrolling interests	(420)	(496)	(83)	(302)	(2,015)	(4,225)	(3,743)	(2,792)	(1,301)	(12,775)	(7,794)
Net Income Attributable to W. P. Carey	$ 129,372	$ 41,339	$ 66,038	$ 68,494	$ 193,263	$ 77,348	$ 75,681	$ 65,274	$ 305,243	$ 411,566	$ 277,289
Earnings per share attributable to W. P. Carey:
Basic (usd per share)	$ 0.75	$ 0.24	$ 0.39	$ 0.41	$ 1.33	$ 0.71	$ 0.70	$ 0.60	$ 1.78	$ 3.50	$ 2.56
Diluted (usd per share)	$ 0.75	$ 0.24	$ 0.38	$ 0.41	$ 1.33	$ 0.71	$ 0.70	$ 0.60	$ 1.78	$ 3.49	$ 2.56