Accounting Standards and Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2018	Jul. 31, 2017	Jan. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, amortization period			5 years
Sales commissions capitalized as contract costs	$ 8,500,000	$ 5,300,000	$ 14,200,000	$ 9,500,000
Amortization of capitalized contract costs	5,000,000	3,700,000	9,600,000	7,000,000
Capitalized contract cost, impairment loss	$ 0	$ 0	$ 0	$ 0
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract duration			1 year
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract duration			5 years
Calculated under Revenue Guidance in Effect before Topic 606 | Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, amortization period					1 year
Calculated under Revenue Guidance in Effect before Topic 606 | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, amortization period					3 years