Schedule of Earnings Per Share Calculation, Error Corrections and Prior Period Adjustments (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
For earnings (loss) per share - basic:
Net loss attributable to Iconix Brand Group, Inc.	$ (111,513)	$ (100,521)
Net income (loss) attributable to Iconix Brand Group, Inc. after accretion of redeemable non- controlling interest for basic earnings (loss) per share	(111,513)	(100,521)
For earnings (loss) per share - diluted:
Net loss attributable to Iconix Brand Group, Inc.	(111,513)	(100,521)
Net loss attributable to Iconix Brand Group, Inc. after the effect of potential conversion of 5.75% Convertible Notes for diluted earnings (loss) per share	$ (111,513)	$ (100,521)
Basic	$ (10.56)	$ (14.93)
Diluted	$ (10.56)	$ (14.93)
Weighted average number of common shares outstanding:
Basic	10,559	6,734
Diluted	10,559	6,734
Previously Presented
For earnings (loss) per share - basic:
Net loss attributable to Iconix Brand Group, Inc.		$ (100,521)
Accretion of redeemable non-controlling interest		(5,432)
Net income (loss) attributable to Iconix Brand Group, Inc. after accretion of redeemable non- controlling interest for basic earnings (loss) per share		(105,953)
For earnings (loss) per share - diluted:
Net loss attributable to Iconix Brand Group, Inc.		(100,521)
Accretion of redeemable non-controlling interest		(5,432)
Net loss attributable to Iconix Brand Group, Inc. after the effect of potential conversion of 5.75% Convertible Notes for diluted earnings (loss) per share		$ (105,953)
Basic		$ (15.73)
Diluted		$ (15.73)
Weighted average number of common shares outstanding:
Basic		6,734
Diluted		6,734