Schedule of Impact on Earnings Per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
For earnings (loss) per share - basic:
Net income (loss) from continuing operations attributable to Iconix Brand Group, Inc.	$ 27,756	$ 4,402
Accretion of redeemable non-controlling interest	(2,483)	(1,026)
Net income (loss) attributable to Iconix Brand Group, Inc. after accretion of redeemable non- controlling interest for basic earnings (loss) per share	25,273	3,376
Net income (loss) from discontinued operations attributable to Iconix Brand Group, Inc.		(8,682)
Net income (loss) attributable to Iconix Brand Group, Inc. for basic earnings (loss) per share	$ 25,273	$ (5,306)
Continuing operations	$ 0.43	$ 0.06
Discontinued operations		(0.15)
Earnings (loss) per share - basic	$ 0.43	$ (0.09)
For earnings (loss) per share - diluted:
Net income (loss) from continuing operations attributable to Iconix Brand Group, Inc.	$ 27,756	$ 4,402
Effect of potential conversion of 5.75% Convertible Notes	(16,280)
Accretion of redeemable non-controlling interest	(2,483)	(1,026)
Net loss attributable to Iconix Brand Group, Inc. after the effect of potential conversion of 5.75% Convertible Notes and accretion of redeemable non- controlling interest for diluted earnings (loss) per share	8,993	3,376
Net income (loss) from discontinued operations attributable to Iconix Brand Group, Inc.		(8,682)
Net loss attributable to Iconix Brand Group, Inc. for diluted earnings (loss) per share	$ 8,993	$ (5,306)
Continuing operations	$ 0.11	$ 0.06
Discontinued operations		(0.15)
Earnings (loss) per share - diluted	$ 0.11	$ (0.09)
Weighted average number of common shares outstanding:
Basic	59,117	56,964
Diluted	82,352	56,964