Deferred Costs - Additional Information (Detail) - USD ($)	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018		Jan. 31, 2017
Deferred Costs [Abstract]
Deferred costs	$ 30,869,000	$ 30,306,000	[1]
Amortization of deferred costs	18,378,000	16,647,000	[1]	$ 14,187,000	[1]
Impairment losses recorded in relation to the costs capitalized	$ 0	$ 0		$ 0

[1] See note 1 of the notes to the consolidated financial statements for a summary of adjustments.