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, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Earnings Per Share [Abstract]
Net income attributable to G-III	$ 87,156	$ 80,615	$ 106,369	$ 88,141
Basic net income per share:
Basic common shares	45,311	44,822	45,117	42,740
Basic net income per share (in dollars per share)	$ 1.92	$ 1.80	$ 2.36	$ 2.06
Diluted net income per share:
Basic common shares	45,311	44,822	45,117	42,740
Restricted stock awards and stock options	1,215	902	1,275	942
Diluted common shares	46,526	45,724	46,392	43,682
Diluted net income per share (in dollars per share)	$ 1.87	$ 1.76	$ 2.29	$ 2.02