Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands		Total	Class A & B common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect adjustment for Topic 842 adoption	[1]	$ (657)			$ (657)
Beginning balance at Jan. 31, 2019		1,237,749	$ 1	$ 617,623	619,197	$ 928
Beginning balance (in shares) at Jan. 31, 2019			146,190,079
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)			526,054
Issuance of common stock upon exercise of stock options		3,439		3,439
Issuance of common stock upon vesting of restricted stock units (in shares)			314,331
Stock-based compensation expense		20,863		20,863
Other comprehensive income		260				260
Net income		73,449			73,449
Ending balance at Apr. 30, 2019		1,335,103	$ 1	641,925	691,989	1,188
Ending balance (in shares) at Apr. 30, 2019			147,030,464
Beginning balance at Jan. 31, 2020		$ 1,665,594	$ 1	745,475	919,658	460
Beginning balance (in shares) at Jan. 31, 2020			149,095,583
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options (in shares)		645,515	645,515
Issuance of common stock upon exercise of stock options		$ 10,279	$ 1	10,278
Issuance of common stock upon vesting of restricted stock units (in shares)			288,949
Stock-based compensation expense		36,907		36,907
Other comprehensive income		1,686				1,686
Net income		86,570			86,570
Ending balance at Apr. 30, 2020		$ 1,801,036	$ 2	$ 792,660	$ 1,006,228	$ 2,146
Ending balance (in shares) at Apr. 30, 2020			150,030,047

[1] We adopted ASU 2016-02, “Leases” (Topic 842) using the modified retrospective method as of February 1, 2019 and elected the transition option that allows us not to restate the comparative periods in our financial statements in the year of adoption.