Financial Instruments (Narrative) (Details) - USD ($)	3 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Jan. 31, 2020
Investments, All Other Investments [Abstract]
Securities in a continuous unrealized loss position for more than 12 months	$ 0		$ 0
Allowance for credit loss	0
Securities, writeoff	0
Gain (loss) from sale or redemption of available for sale securities	0	$ 0
Proceeds from sale and maturity of marketable securities	0	$ 4,600,000
Direct investments in privately held companies	$ 148,500,000		$ 122,500,000