Stock-Based Compensation - Restricted Stock (Details) - Restricted stock and restricted stock units	9 Months Ended
	Oct. 31, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Balance as of January 31, 2019 (in shares) | shares	7,703,705
Granted - restricted stock and restricted stock units (in shares) | shares	5,539,182
Vested and converted to shares (in shares) | shares	(2,238,010)
Canceled (in shares) | shares	(1,183,162)
Balance as of October 31, 2019 (in shares) | shares	9,821,715
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Balance as of January 31, 2019 (in dollars per share) | $ / shares	$ 16.07
Granted - restricted stock and restricted stock units (in dollars per share) | $ / shares	19.83
Vested and converted to shares (in dollars per share) | $ / shares	15.93
Canceled (in dollars per share) | $ / shares	19.11
Balance as of October 31, 2019 (in dollars per share) | $ / shares	$ 17.86