Employee Incentive Plans - Schedule of Restricted Stock Unit Activity (Details) - Restricted stock units	3 Months Ended
	Apr. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Beginning balance (in shares) | shares	2,862,929
Granted during period (in shares) | shares	717,630
Vested during period (in shares) | shares	(58,825)
Forfeited during period (in shares) | shares	(89,180)
Ending balance (in shares) | shares	3,432,554
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Beginning balance (in dollars per share) | $ / shares	$ 24.38
Granted during period (in dollars per share) | $ / shares	39.97
Vested during period (in dollars per share) | $ / shares	17.00
Forfeited during period (in dollars per share) | $ / shares	24.74
Ending balance (in dollars per share) | $ / shares	$ 27.75