Deferred Costs - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
	Oct. 31, 2018	Oct. 31, 2017		Oct. 31, 2018	Oct. 31, 2017		Jan. 31, 2018	[1]
Deferred Costs [Abstract]
Deferred costs	$ 28,035,000			$ 28,035,000			$ 30,306,000
Amortization of deferred costs	4,595,000	$ 4,203,000	[1]	13,697,000	$ 12,338,000	[1]
Impairment loss recorded in relation to the costs capitalized	$ 0	$ 0		$ 0	$ 0

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