Net Income per Common Share - Reconciliation between basic and diluted net income per share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Earnings Per Share [Abstract]
Net income attributable to G-III	$ 80,615	$ 59,595	$ 88,141	$ 64,305
Basic net income per share:
Basic common shares	22,411	20,399	21,370	20,290
Basic net income per share (in dollars per share)	$ 3.60	$ 2.92	$ 4.12	$ 3.17
Diluted net income per share:
Basic common shares	22,411	20,399	21,370	20,290
Restricted stock awards and stock options	451	512	471	528
Diluted common shares	22,862	20,911	21,841	20,818
Diluted net income per share (in dollars per share)	$ 3.53	$ 2.85	$ 4.04	$ 3.09