Schedule of Impact on Earnings Per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
For earnings (loss) per share - basic:
Net income attributable to Iconix Brand Group, Inc.	$ (35,708)	$ 20,224	$ (16,492)	$ (31,446)
Net income attributable to Iconix Brand Group, Inc. after the effect of accretion of redeemable non-controlling interest for basic earnings (loss) per share	(35,708)	20,224	(16,492)	(31,446)
For earnings (loss) per share - diluted:
Net income attributable to Iconix Brand Group, Inc.	(35,708)	20,224	(16,492)	(31,446)
Effect of potential conversion of 5.75% Convertible Notes		(15,641)		(59,066)
Net income attributable to Iconix Brand Group, Inc. after the effect of potential conversion of 5.75% Convertible Notes for diluted earnings (loss) per share	$ (35,708)	$ 4,583	$ (16,492)	$ (90,512)
Basic	$ (3.07)	$ 2.81	$ (1.62)	$ (4.87)
Diluted	$ (3.07)	$ 0.26	$ (1.62)	$ (7.35)
Weighted average number of common shares outstanding:
Basic	11,631	7,184	10,169	6,458
Diluted	11,631	17,591	10,169	12,310