Segment Reporting - Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information, Profit (Loss)
Revenues	$ 43,928	$ 49,027	$ 86,808	$ 99,321
Operating expenses	(30,582)	(34,021)	(66,810)	(66,293)
Interest expense	(10,354)	(12,044)	(20,843)	(24,401)
Other gains and (losses)	905	699	(1,221)	223
Gain on sale of real estate, net	0	650	0	16,058
(Provision for) benefit from income taxes	(1,558)	867	(1,164)	(57)
Net income attributable to noncontrolling interests	(3,530)	(2,100)	(6,141)	(6,946)
Net (Loss) Income Attributable to CPA:18 – Global	(1,191)	3,078	(9,371)	17,905
Operating Segments | Net Lease
Segment Reporting Information, Profit (Loss)
Revenues	26,538	30,731	50,605	61,723
Operating expenses	(15,421)	(18,638)	(36,023)	(35,949)
Interest expense	(6,743)	(8,694)	(13,601)	(17,430)
Other gains and (losses)	224	503	(3,216)	546
Gain on sale of real estate, net	0	650	0	1,547
(Provision for) benefit from income taxes	(1,341)	1,366	(702)	1,006
Net income attributable to noncontrolling interests	(1,526)	(45)	(2,226)	(254)
Net (Loss) Income Attributable to CPA:18 – Global	1,731	5,873	(5,163)	11,189
Operating Segments | Self Storage
Segment Reporting Information, Profit (Loss)
Revenues	14,670	15,167	30,026	30,006
Operating expenses	(9,080)	(8,872)	(18,175)	(17,617)
Interest expense	(3,374)	(3,450)	(6,730)	(6,876)
Other gains and (losses)	(155)	(607)	(209)	(1,275)
(Provision for) benefit from income taxes	(17)	(11)	(48)	(44)
Net (Loss) Income Attributable to CPA:18 – Global	2,044	2,227	4,864	4,194
Operating Segments | Other Operating Properties
Segment Reporting Information, Profit (Loss)
Revenues	2,010	2,307	4,757	4,929
Operating expenses	(1,324)	(1,544)	(2,809)	(3,178)
Interest expense	(192)	166	(444)	46
Other gains and (losses)	4	(5)	19	(44)
Gain on sale of real estate, net	0	0	0	14,514
(Provision for) benefit from income taxes	38	(356)	52	(379)
Net income attributable to noncontrolling interests	25	50	30	(2,739)
Net (Loss) Income Attributable to CPA:18 – Global	561	618	1,605	13,149
All Other
Segment Reporting Information, Profit (Loss)
Revenues	710	822	1,420	2,655
Operating expenses	0	0	0	(1)
Net (Loss) Income Attributable to CPA:18 – Global	710	822	1,420	2,654
Corporate
Segment Reporting Information, Profit (Loss)
Net income attributable to noncontrolling interests	(2,029)	(2,105)	(3,945)	(3,953)
Unallocated Corporate Income and Expenses	$ (4,208)	$ (4,357)	$ (8,152)	$ (9,328)