Deferred Costs - Additional Information (Detail) - USD ($)	3 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Jan. 31, 2019
Deferred Costs [Abstract]
Deferred costs	$ 30,621,000		$ 30,869,000
Amortization of deferred costs	4,849,000	$ 4,519,000
Impairment losses recorded in relation to the costs capitalized	$ 0	$ 0