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	$ 211,720	$ 198,292	$ 196,711	$ 187,468	$ 144,515	$ 118,988	$ 112,979	$ 103,459	$ 794,191		$ 479,941		$ 372,293
Gross profit	155,209	140,664	139,581	126,235	103,860	89,012	80,847	70,108	561,689	[1],[2]	343,827	[1],[2]	214,258	[1],[2]
Loss from operations	(64,437)	(82,467)	(89,097)	(103,753)	(86,965)	(25,673)	(29,424)	(51,702)	(339,754)		(193,764)		(374,172)
Net loss	$ (64,287)	$ (82,122)	$ (87,043)	$ (103,130)	$ (85,521)	$ (25,857)	$ (28,949)	$ (52,322)	$ (336,582)		$ (192,649)		$ (369,672)
Net loss per share, basic and diluted (in dollars per share)	$ (0.22)	$ (0.29)	$ (0.31)	$ (0.38)	$ (0.45)	$ (0.17)	$ (0.19)	$ (0.36)	$ (1.20)		$ (1.21)		$ (3.24)

[1] Amounts include amortization of acquired intangible assets as follows (in thousands):

[2] Amounts include stock-based compensation expense as follows (in thousands):