Accounting Standards and Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended		12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Jan. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, amortization period	5 years
Capitalized contract costs	$ 5,600,000	$ 4,200,000
Amortization of capitalized contract costs	4,600,000	3,400,000
Capitalized contract cost, impairment loss	$ 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