XML 48 R37.htm IDEA: XBRL DOCUMENT v3.10.0.1
Short-Term Investments - Schedule of Short-Term Investments (Detail) - USD ($)
$ in Thousands
Oct. 31, 2018
Jan. 31, 2018
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost $ 585,775 $ 443,272
Available-for-sale securities, Gross unrealized gains 41 7
Available-for-sale securities, Gross unrealized losses (1,533) (1,500)
Available-for-sale securities, Estimated fair value 584,283 441,779 [1]
Certificates of deposits [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 9,540  
Available-for-sale securities, Gross unrealized gains 8  
Available-for-sale securities, Gross unrealized losses (1)  
Available-for-sale securities, Estimated fair value 9,547  
Asset-backed securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 80,663 67,875
Available-for-sale securities, Gross unrealized gains 3  
Available-for-sale securities, Gross unrealized losses (502) (424)
Available-for-sale securities, Estimated fair value 80,164 67,451
Commercial paper [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 4,969 19,926
Available-for-sale securities, Gross unrealized losses   (12)
Available-for-sale securities, Estimated fair value 4,969 19,914
Corporate notes and bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 172,815 160,499
Available-for-sale securities, Gross unrealized gains 30 1
Available-for-sale securities, Gross unrealized losses (758) (759)
Available-for-sale securities, Estimated fair value 172,087 159,741
Foreign government bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 3,001 1,504
Available-for-sale securities, Gross unrealized losses (20) (18)
Available-for-sale securities, Estimated fair value 2,981 1,486
Mortgage backed securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 6,133 11,555
Available-for-sale securities, Gross unrealized losses (14) (75)
Available-for-sale securities, Estimated fair value 6,119 11,480
U.S. agency obligations [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 35,744 71,206
Available-for-sale securities, Gross unrealized gains   1
Available-for-sale securities, Gross unrealized losses (21) (76)
Available-for-sale securities, Estimated fair value 35,723 71,131
U.S. treasury securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 272,910 110,707
Available-for-sale securities, Gross unrealized gains   5
Available-for-sale securities, Gross unrealized losses (217) (136)
Available-for-sale securities, Estimated fair value $ 272,693 $ 110,576
[1] See note 1 of the notes to the condensed consolidated financial statements for a summary of adjustments.