Convertible Senior Notes (Tables)
 3 Months Ended
Apr. 30, 2019
Debt Disclosure [Abstract]  
Convertible debt schedules
The net carrying amount of the liability component of the Notes was as follows (in thousands):
 
April 30, 2019
Principal
$
300,000

Unamortized debt discount
(74,178
)
Unamortized debt issuance costs
(5,743
)
Net carrying amount
$
220,079

The net carrying amount of the equity component of the Notes was as follows (in thousands):
 
April 30, 2019
Debt discount for conversion option
$
84,168

Issuance costs
(2,485
)
Net carrying amount
$
81,683
Interest expense related to Notes
The following table sets forth the interest expense related to the Notes (in thousands):
 
Three Months Ended April 30,
 
2019
 
2018
Contractual interest expense
$
563

 
$
—

Amortization of debt discount
3,033

 
—

Amortization of issuance costs
188

 
—

Total
$
3,784

 
$
—