Accounting Standards and Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, amortization period	5 years		5 years
Sales commissions capitalized as contract costs	$ 11,700,000	$ 6,700,000	$ 25,900,000	$ 16,200,000
Amortization of capitalized contract costs	5,400,000	3,900,000	15,000,000	10,900,000
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		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		3 years