Convertible Senior Notes (Tables)
 3 Months Ended
Apr. 30, 2019
Debt Disclosure [Abstract]  
Schedule of convertible debt
The net carrying value of the liability component of the Notes was as follows:
(in thousands)
April 30, 2019
Principal
$
575,000

Less: unamortized debt discount
(119,903
)
Less: unamortized transaction costs
(9,712
)
Net carrying amount
$
445,385


The net carrying amount of the equity component of the Notes was as follows:
(in thousands)
April 30, 2019
Proceeds allocated to the conversion option (debt discount)
$
134,667

Less: transaction costs
(3,336
)
Net carrying amount
$
131,331


The interest expense recognized related to the Notes was as follows:
(in thousands)
Three Months Ended April 30, 2019
Contractual interest expense
$
710

Amortization of debt discount
484

Amortization of transaction costs
5,970

Total
$
7,164