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		9 Months Ended
	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2021	Oct. 31, 2020
Net Income (Loss) per Common Share
Net income attributable to G-III Apparel Group, Ltd.	$ 106,674	$ 63,174	$ 152,163	$ 8,903
Basic net income (loss) per share:
Basic common shares	48,567	48,359	48,474	48,201
Basic net income (loss) per share (in dollars per share)	$ 2.20	$ 1.31	$ 3.14	$ 0.18
Diluted net income (loss) per share:
Basic common shares	48,567	48,359	48,474	48,201
Diluted restricted stock awards and stock options	891	450	1,025	388
Diluted common shares	49,458	48,809	49,499	48,589
Diluted net income (loss) per share (in dollars per share)	$ 2.16	$ 1.29	$ 3.07	$ 0.18