Basis of Presentation and Summary of Significant Accounting Policies - Recently Adopted Accounting Standards (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018		Jan. 31, 2017		Feb. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred commissions, current	$ 29,244	$ 21,088	[1]
Decrease in loss from operations	169,257	167,434	[2]	$ 221,272	[2]
Deferred commissions, non-current	85,729	66,225	[1]
Sales commission expenses	$ 118,400	$ 102,900		$ 71,300
Expected Commission (as a percent)	25.00%
Subsequent Event
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						$ 125,000
Subsequent Event | Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finance Lease, Right-of-Use Asset						$ 131,000

[1] * As adjusted to reflect the impact of the full retrospective adoption of ASC 606

[2] *As adjusted to reflect the impact of the full retrospective adoption of ASC 606 - see Note 2.