Net Income (Loss) 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, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to G-III	$ 70,564	$ 87,156	$ 72,042	$ 106,369
Basic net income per share:
Basic common shares	45,918	45,311	45,713	45,117
Basic net income per share (in dollars per share)	$ 1.54	$ 1.92	$ 1.58	$ 2.36
Diluted net income per share:
Basic common shares	45,918	45,311	45,713	45,117
Diluted Restricted stock awards and stock options	984	1,215	1,234	1,275
Diluted common shares	46,902	46,526	46,947	46,392
Diluted net income per share (in dollars per share)	$ 1.50	$ 1.87	$ 1.53	$ 2.29