Segment Reporting - Total Company (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting [Abstract]
Revenues	$ 307,371	$ 302,419	$ 290,530	$ 308,999	$ 311,227	$ 318,005	$ 305,211	$ 298,323	$ 1,209,319	$ 1,232,766	$ 885,732
Operating expenses	177,996	162,239	158,379	192,987	175,816	198,409	179,170	177,722	691,601	731,117	526,451
Other income and expenses									(72,522)	(168,894)	79,471
Benefit from (provision for) income taxes									20,759	(26,211)	(14,411)
Net income attributable to noncontrolling interests	(43)	(37)	(9,904)	(612)	(420)	(496)	(83)	(302)	(10,596)	(1,301)	(12,775)
Net income attributable to W. P. Carey	$ 134,572	$ 149,397	$ 105,300	$ 66,090	$ 129,372	$ 41,339	$ 66,038	$ 68,494	$ 455,359	$ 305,243	$ 411,566