Schedule of Impact on Earnings Per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
For earnings (loss) per share - basic:
Net income attributable to Iconix Brand Group, Inc.	$ (21,483)	$ 17,945
Accretion of redeemable non-controlling interest	(394)
Net income attributable to Iconix Brand Group, Inc. after the effect of accretion of redeemable non-controlling interest for basic earnings (loss) per share	(21,877)	17,945
For earnings (loss) per share - diluted:
Net income attributable to Iconix Brand Group, Inc.	(21,483)	17,945
Effect of potential conversion of 5.75% Convertible Notes		(18,244)
Accretion of redeemable non-controlling interest	(394)
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	$ (21,877)	$ (299)
Basic	$ (1.86)	$ 2.12
Diluted	$ (1.86)	$ (0.01)
Weighted average number of common shares outstanding:
Basic	11,772	8,465
Diluted	11,772	44,786