Equity Incentive Plans - Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jul. 31, 2018	Jan. 31, 2017	Apr. 04, 2018	Jan. 31, 2018
Options Outstanding, Number of Shares
Beginning balance (in shares)	46,359,949
Options exercised (in shares)	(5,884,173)
Options forfeited/cancelled (in shares)	(1,191,720)
Ending balance (in shares)	39,284,056
Options Outstanding, Number of Shares, Vested and exercisable (in shares)	26,675,832
Options Outstanding, Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 7.75
Options exercised (in dollars per share)	4.94
Options forfeited/cancelled (in dollars per share)	9.36
Ending balance (in dollars per share)	8.12
Weighted Average Exercise Price, Vested and exercisable (in dollars per share)	$ 6.00
Weighted- Average Remaining Contractual Life
Weighted Average Remaining Contractual Life	5 years 10 months 24 days	6 years 3 months 18 days
Weighted Average Remaining Contractual Life, Vested and exercisable	5 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 531,664			$ 574,224
Aggregate Intrinsic Value, Vested and exercisable	$ 417,651
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing price of stock (in dollars per share)	$ 21.66
Unrecognized compensation cost, stock options	$ 49,600
Compensation cost, weighted average term	2 years 1 month 6 days
Class A
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Closing price of stock (in dollars per share)	$ 21.66		$ 19.83