Employee Benefits and Stock-based Compensation - Restricted Stock and Restricted Stock Units Activities (Detail) - Restricted stock and restricted stock units [Member] - $ / shares	12 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested, beginning balance	2,617,266	2,395,516	2,103,281
Shares, Granted	1,499,203	1,329,288	1,367,751
Shares, Vested	(1,162,883)	(1,012,581)	(994,500)
Shares, Forfeited	(81,785)	(94,957)	(81,016)
Shares, Unvested, ending balance	2,871,801	2,617,266	2,395,516
Weighted-Average Grant-Date Fair Value, Unvested, beginning balance	$ 50.30	$ 48.49	$ 56.45
Weighted-Average Grant-Date Fair Value, Granted	53.45	54.54	40.03
Weighted-Average Grant-Date Fair Value, Vested	50.53	51.24	53.27
Weighted-Average Grant-Date Fair Value, Forfeited	54.48	54.26	53.57
Weighted-Average Grant-Date Fair Value, Unvested, ending balance	$ 51.73	$ 50.30	$ 48.49