Selected Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013
Interim Period
Revenues	$ 20,094	$ 14,882	$ 12,647	$ 6,694	$ 2,345	$ 947	$ 0	$ 0	$ 41,383	$ 3,262
Operating expenses	41,361	18,580	12,099	23,091	1,635	604	65	0	95,131	2,304
Net loss from continuing operations before income taxes	(25,538)	(9,465)	(3,110)	(18,443)	(104)	(72)	(65)	0	(56,556)	(241)
Net income attributable to noncontrolling interests	(700)	(1,136)	(1,248)	3,773	(324)	(66)	0	0	689	(390)
Net Loss Attributable to CPA®:18 – Global	(26,238)	(10,601)	(4,358)	(14,670)	(428)	(138)	(65)	0	(55,867)	(631)
Class A common stock
Interim Period
Net Loss Attributable to CPA®:18 – Global									(49,494)	(496)
Common Stock
Net loss per share (in dollars per share)	$ (0.22)	$ (0.10)	$ (0.05)	$ (0.35)	$ (0.03)	$ (0.18)	$ (2.81)	$ 0.00	$ (0.63)	$ (0.18)
Weighted-average shares outstanding	99,836,316	99,007,256	77,300,223	38,001,011	10,469,534	616,292	23,222	0	78,777,525	2,792,648
Distributions declared per share (in dollars per share)	$ 0.1562	$ 0.1562	$ 0.1562	$ 0.1562	$ 0.1562	$ 0.1155	$ 0.0000	$ 0.0000	$ 0.6248	$ 0.2717
Class C common stock
Interim Period
Net Loss Attributable to CPA®:18 – Global									$ (6,373)	$ (135)
Common Stock
Net loss per share (in dollars per share)	$ (0.25)	$ (0.12)	$ (0.07)	$ (0.37)	$ (0.05)	$ (0.20)	$ 0.00	$ 0.00	$ (0.72)	$ (0.27)
Weighted-average shares outstanding	15,376,487	9,925,481	6,126,012	3,820,432	1,825,374	149,294	0	0	8,847,966	497,725
Distributions declared per share (in dollars per share)	$ 0.1329	$ 0.1329	$ 0.1329	$ 0.1329	$ 0.1329	$ 0.0982	$ 0.0000	$ 0.0000	$ 0.5316	$ 0.2311