Financial Instruments - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 31, 2021	Jul. 31, 2020	Jul. 31, 2021	Jul. 31, 2020	Jan. 31, 2021
Investments, All Other Investments [Abstract]
Securities in a continuous unrealized loss position for more than 12 months	$ 0		$ 0		$ 0
Allowance for credit loss	0		0		0
Securities, writeoff			0	$ 0
Gain (loss) from sale or redemption of available for sale securities			0	0
Sales and maturities of marketable securities	0	$ 11,000,000	4,000,000.0	11,000,000
Direct investments in privately held companies	129,500,000		129,500,000		$ 134,100,000
Equity method investment, realized gain (loss) on disposal	$ 0	$ 0	$ 8,100,000	$ 0