Goodwill and Trademarks and Other Intangibles, net - Additional Information (Detail)		1 Months Ended		3 Months Ended					9 Months Ended	12 Months Ended
	Oct. 15, 2018 USD ($)	Jul. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Jul. 31, 2018 USD ($)	Dec. 31, 2016 USD ($)
Intangible Assets By Major Class [Line Items]
Goodwill				$ 26,099,000			$ 63,882,000			$ 26,099,000	$ 63,882,000		$ 171,250,000
Number of reportable segments | Segment										4
Non-cash impairment charge				0		$ 37,800,000	0	$ 103,900,000		$ 37,812,000	103,877,000
Impairment of intangible assets, indefinite-lived										136,417,000	525,726,000
Non-cash asset impairment charge										1,777,000
Trademarks and other intangibles, net				337,700,000			465,722,000			337,700,000	465,722,000
Amortization expense for intangible assets										258,000	741,000
Projects amortization expenses, 2021				0						0
Projects amortization expenses, 2022				0						0
Projects amortization expenses, 2023				0						0
Iconix SE Asia, Ltd.
Intangible Assets By Major Class [Line Items]
Increase (Decrease) in indefinite-lived trademarks			$ (22,700,000)
Mossimo License Agreement | Target
Intangible Assets By Major Class [Line Items]
License agreement expiration date									2018-10
DanskinNow License Agreement | Walmart
Intangible Assets By Major Class [Line Items]
License agreement expiration date									2019-01
Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of the definite-lived trademarks										0	0
Trademarks
Intangible Assets By Major Class [Line Items]
Trademarks and other intangibles, net					$ 12,300,000
Increase (Decrease) in indefinite-lived trademarks			(204,300,000)
Trademarks | NGX
Intangible Assets By Major Class [Line Items]
Increase (Decrease) in indefinite-lived trademarks		$ (5,000,000)
Trademarks | Peanuts Holdings, LLC
Intangible Assets By Major Class [Line Items]
Increase (Decrease) in indefinite-lived trademarks			(153,600,000)
Trademarks | Strawberry Shortcake
Intangible Assets By Major Class [Line Items]
Increase (Decrease) in indefinite-lived trademarks			$ (50,700,000)
Operating Segments | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				58,700,000							521,800,000
Women's
Intangible Assets By Major Class [Line Items]
Goodwill							37,812,000				37,812,000		111,751,000
Non-cash impairment charge						37,800,000				37,812,000	73,939,000
Women's | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived	$ 0			32,700,000	$ 4,400,000	$ 73,300,000
Women's | Joe Boxer Trademark
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				6,800,000
Women's | Operating Segments
Intangible Assets By Major Class [Line Items]
Non-cash impairment charge											73,900,000
Women's | Operating Segments | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				55,100,000							227,600,000
Men's
Intangible Assets By Major Class [Line Items]
Goodwill													1,524,000
Non-cash impairment charge											1,524,000
Men's | Operating Segments
Intangible Assets By Major Class [Line Items]
Non-cash impairment charge											1,500,000
Men's | Operating Segments | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				100,000							135,900,000
Home
Intangible Assets By Major Class [Line Items]
Goodwill													28,414,000
Non-cash impairment charge											28,414,000
Non-cash asset impairment charge							4,100,000
Home | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				2,700,000
Home | Operating Segments
Intangible Assets By Major Class [Line Items]
Non-cash impairment charge											28,400,000
Home | Operating Segments | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				2,700,000							69,500,000
International
Intangible Assets By Major Class [Line Items]
Goodwill				26,099,000			$ 26,070,000			$ 26,099,000	26,070,000		$ 29,561,000
International | Operating Segments | Trademarks
Intangible Assets By Major Class [Line Items]
Impairment of intangible assets, indefinite-lived				$ 800,000							$ 88,800,000
Iconix Australia
Intangible Assets By Major Class [Line Items]
Ownership interest acquired					5.00%							5.00%
Goodwill												$ 29,000
Iconix Australia | International
Intangible Assets By Major Class [Line Items]
Ownership interest acquired				5.00%						5.00%
Maximum
Intangible Assets By Major Class [Line Items]
Projects amortization expenses, 2019				$ 100,000						$ 100,000
Projects amortization expenses, 2020				$ 100,000						$ 100,000
Maximum | Iconix Australia
Intangible Assets By Major Class [Line Items]
Goodwill												$ 100,000