Deferred Costs - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Deferred Costs [Abstract]
Deferred costs	$ 35,472,000		$ 35,472,000		$ 35,585,000
Amortization of deferred costs	5,000,000	$ 5,000,000	15,000,000	$ 15,000,000
Impairment losses recorded in relation to the costs capitalized	$ 0	$ 0	$ 0	$ 0