Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Data
Revenues	$ 196,961	$ 210,754	$ 221,528	$ 219,059	$ 228,780	$ 225,247	$ 217,266	$ 270,240	$ 848,302	$ 941,533	$ 938,383
Expenses	111,711	115,164	127,991	134,882	144,564	136,472	160,697	180,000	489,748	621,733	580,829
Net income	74,473	83,654	67,131	59,825	48,470	112,302	53,171	60,864	285,083	274,807	185,227
Net income attributable to noncontrolling interests	736	(3,376)	(2,813)	(2,341)	(766)	(1,359)	(1,510)	(3,425)	(7,794)	(7,060)	(12,969)
Net Income Attributable to W. P. Carey	$ 75,209	$ 80,278	$ 64,318	$ 57,484	$ 47,704	$ 110,943	$ 51,661	$ 57,439	$ 277,289	$ 267,747	$ 172,258
Earnings per share attributable to W. P. Carey:
Basic (usd per share)	$ 0.69	$ 0.74	$ 0.60	$ 0.53	$ 0.44	$ 1.03	$ 0.48	$ 0.54
Diluted (usd per share)	0.69	0.74	0.59	0.53	0.44	1.03	0.48	0.54
Distributions declared per share (usd per share)	$ 1.01	$ 1.005	$ 1	$ 0.995	$ 0.99	$ 0.985	$ 0.98	$ 0.9742	$ 4.01	$ 3.9292	$ 3.8261