Summary of Significant Accounting Policies - Long-Lived Assets, Including Goodwill and Other Acquired Intangible Assets (Details) - USD ($)	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017
Accounting Policies [Abstract]
Goodwill impairment	$ 0	$ 0
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life		2 years 9 months 18 days
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted average useful life		3 years 2 months 12 days