SIGNIFICANT ACCOUNTING POLICIES - Reconciliation between Basic and Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Accounting Policies [Abstract]
Net income (loss) attributable to G-III (in dollars)	$ (20,104)	$ 70,564	$ (1,293)	$ 2,771	$ 7,964	$ 87,156	$ 12,453	$ 6,760	$ 51,938	$ 114,333	$ 110,361
Basic net income per share:
Basic common shares									46,308	45,328	43,298
Basic net income per share	$ (0.42)	$ 1.54	$ (0.03)	$ 0.06	$ 0.17	$ 1.92	$ 0.28	$ 0.15	$ 1.12	$ 2.52	$ 2.55
Diluted net income per share:
Basic common shares									46,308	45,328	43,298
Stock options and restricted stock awards									1,086	1,184	1,126
Diluted common shares									47,394	46,512	44,424
Diluted net income per share	$ (0.42)	$ 1.50	$ (0.03)	$ 0.06	$ 0.17	$ 1.87	$ 0.27	$ 0.15	$ 1.10	$ 2.46	$ 2.48