Net Income per Common Share - Reconciliation between basic and diluted net income per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020
Net Income (Loss) per Common Share
Net income attributable to G-III Apparel Group, Ltd.	$ 19,168	$ (14,976)	$ 45,489	$ (54,271)
Basic net income (loss) per share:
Basic common shares	48,476	48,214	48,427	48,121
Basic net income (loss) per share (in dollars per share)	$ 0.40	$ (0.31)	$ 0.94	$ (1.13)
Diluted net income (loss) per share:
Basic common shares	48,476	48,214	48,427	48,121
Diluted restricted stock awards and stock options	1,047		1,075
Diluted common shares	49,523	48,214	49,502	48,121
Diluted net income (loss) per share (in dollars per share)	$ 0.39	$ (0.31)	$ 0.92	$ (1.13)