Income Taxes - Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Deferred Tax Assets, Valuation Allowance [Roll Forward]
Beginning balance	$ 282,141	$ 119,153	$ 133,029
Valuation allowance charged to income tax provision	163,605	201,646	56,566
Adoption of new accounting principle	0	0	5,610
Valuation allowance credited as a result of U.S. Tax Act	0	0	(59,520)
Convertible senior notes issued	0	(31,594)	0
Acquisition of SpringCM	0	(7,064)	0
Valuation allowance credited to income tax provision	0	0	(16,532)
Ending balance	$ 445,746	$ 282,141	$ 119,153