Selected Quarterly Financial Data - Summary of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 114,270	$ 106,921	$ 98,107	$ 89,923	$ 87,012	$ 83,825	$ 75,664	$ 66,721	$ 409,221	$ 313,222	$ 210,151
Gross profit	74,526	69,909	64,634	57,938	55,856	53,409	47,528	40,771	267,007	197,564	127,549
Operating income	15,211	20,100	22,353	20,925	20,683	19,941	16,785	12,557	78,589	69,966	39,304
Net income	$ 17,590	$ 10,482	$ 13,406	$ 12,982	$ 13,326	$ 10,258	$ 9,578	$ 7,221	$ 54,460	$ 40,383	$ 23,615
Net income per share attributable to Class A and Class B common stockholders:
Basic	$ 0.13	$ 0.08	$ 0.10	$ 0.10	$ 0.10	$ 0.08	$ 0.07	$ 0.06	$ 0.41	$ 0.31	$ 0.20
Diluted	$ 0.12	$ 0.07	$ 0.09	$ 0.09	$ 0.09	$ 0.07	$ 0.07	$ 0.05	$ 0.38	$ 0.28	$ 0.15