Discontinued Operations - Summary of Financial Results of Entertainment Segment (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other expenses (income):
(Loss) Income from operations of discontinued operations before income taxes									$ (26,232)	$ 9,947	$ 29,725
Gain (loss) on sale of Entertainment segment									104,099
Provision for income taxes									28,899	1,631	8,557
Net income from discontinued operations	$ (650)	$ (2,130)	$ 59,127	$ (7,379)	$ (2,465)	$ 2,734	$ 2,582	$ 5,465	48,968	8,316	21,168
Less: Net income attributable to non-controlling interest from discontinued operations									2,943	5,952	6,023
Net income from discontinued operations attributable to Iconix Brand Group, Inc.	$ (656)	$ (2,130)	$ 57,493	$ (8,682)	$ (3,639)	$ 1,036	$ 980	$ 3,987	46,025	2,364	15,145
Operating Segments | Entertainment
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Licensing revenue									53,129	113,318	107,607
Selling, general and administrative expenses									34,542	77,832	70,940
Depreciation and amortization									303	668	403
Trademark impairment										5,128
Operating income									18,284	29,690	36,264
Other expenses (income):
Interest expense									12,973	20,617	6,806
Interest income									(180)	(676)	(855)
Loss on extinguishment of debt									31,554
Foreign currency translation loss (gain)									169	(198)	588
Other expenses – net									44,516	19,743	6,539
(Loss) Income from operations of discontinued operations before income taxes									(26,232)	9,947	29,725
Gain (loss) on sale of Entertainment segment									104,099
Provision for income taxes									28,899	1,631	8,557
Net income from discontinued operations									48,968	8,316	21,168
Less: Net income attributable to non-controlling interest from discontinued operations									2,943	5,952	6,023
Net income from discontinued operations attributable to Iconix Brand Group, Inc.									$ 46,025	$ 2,364	$ 15,145