Cash Equivalents and Short-Term Investments - Schedule of Contractual Maturities of Short-term Investments (Details) - USD ($) $ in Thousands	Jul. 31, 2017	Jan. 31, 2017
Amortized Cost
Amortized cost, due within one year	$ 58,288	$ 12,842
Amortized cost, due between one to five years	28,479	1,538
Investments, amortized cost	86,767	14,380
Estimated Fair Value
Estimated fair value, due within one year	58,276	12,852
Estimated fair value, due between one to five years	28,479	1,538
Estimated fair value total	$ 86,755	$ 14,390