Basis of Presentation and Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017		Oct. 31, 2018	Oct. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 372,779	$ 277,591	[1]	$ 937,608	$ 684,906	[1]
United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	263,488	192,919		678,166	505,045
Rest of the world
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue	$ 109,291	84,672		$ 259,442	179,861
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		277,674			684,766
As Previously Reported | United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		192,977			504,937
As Previously Reported | Rest of the world
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		84,697			179,829
Adjustment | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(83)			140
Adjustment | United States | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		(58)			108
Adjustment | Rest of the world | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total revenue		$ (25)			$ 32

[1] * Prior period information has been adjusted to reflect the adoption impact of ASC 606, which we adopted on February 1, 2018.