Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019	Jan. 31, 2019	Oct. 31, 2018	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 188,251	$ 166,593	$ 145,826	$ 121,988	$ 105,800	$ 90,121	$ 74,526	$ 60,070	$ 622,658	$ 330,517	$ 151,478
Gross profit	155,704	135,748	117,926	97,884	86,275	73,278	61,553	48,410	507,262	269,516	120,698
Income (loss) from operations	10,553	(1,679)	2,265	1,557	5,492	(1,063)	3,422	(1,684)	12,696	6,167	(4,833)
Net income (loss) attributable to common stockholders	$ 15,313	$ 2,207	$ 5,521	$ 198	$ 1,196	$ (598)	$ 496	$ (1,340)	$ 21,750	$ 0	$ (8,227)
Net income (loss) per share attributable to common stockholders:
Basic (in dollars per share)	$ 0.06	$ 0.01	$ 0.02	$ 0.00	$ 0.01	$ (0.01)	$ 0.01	$ (0.02)	$ 0.09	$ 0.00	$ (0.11)
Diluted (in dollars per share)	$ 0.05	$ 0.01	$ 0.02	$ 0.00	$ 0.01	$ (0.01)	$ 0.00	$ (0.02)	$ 0.09	$ 0.00	$ (0.11)