Deferred Costs - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018	Jan. 31, 2019
Deferred Costs [Abstract]
Deferred costs	$ 29,873,000		$ 29,873,000		$ 30,869,000
Amortization of deferred costs	4,832,000	$ 4,595,000	14,524,000	$ 13,697,000
Impairment losses recorded in relation to the costs capitalized	$ 0	$ 0	$ 0	$ 0