Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 31, 2020	Feb. 01, 2019	Jan. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 11,147		$ 0
Operating lease, liability	11,863
Deferred rent liability		$ 1,000
Property and equipment, net	58,316		73,664
Finance lease, right-of-use asset	39,411	43,400
Finance lease, liability	63,890	64,000
Cumulative effect of accounting change	(4,103)
ASC 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets		10,300
Operating lease, liability		11,300	70,200
Deferred rent liability		1,900
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change	$ (4,103)
Accumulated Deficit | ASC 842
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		$ (4,100)
Build-to-suit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Property and equipment, net			$ 55,700