Changes in Accumulated Other Comprehensive Loss by Component, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance			$ 1,300,903
Other comprehensive income (loss) before reclassifications	$ (5,489)	$ (1,399)	(21,426)	$ 9,336
Amounts reclassified from accumulated other comprehensive income (loss)	(3)	(2)	(16)	(11)
Total other comprehensive (loss) income	(5,492)	(1,401)	(21,442)	9,325
Ending Balance	1,460,609	1,284,808	1,460,609	1,284,808
Foreign Currency Translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(26,190)	(23,282)	(10,340)	(34,012)
Other comprehensive income (loss) before reclassifications	(5,358)	(1,388)	(21,208)	9,342
Total other comprehensive (loss) income	(5,358)	(1,388)	(21,208)	9,342
Ending Balance	(31,548)	(24,670)	(31,548)	(24,670)
Unrealized Gains and (Losses) on available- for-Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(411)	(61)	(311)	(57)
Other comprehensive income (loss) before reclassifications	(131)	(11)	(218)	(6)
Amounts reclassified from accumulated other comprehensive income (loss)	(3)	(2)	(16)	(11)
Total other comprehensive (loss) income	(134)	(13)	(234)	(17)
Ending Balance	(545)	(74)	(545)	(74)
Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(26,601)	(23,343)	(10,651)	(34,069)
Ending Balance	$ (32,093)	$ (24,744)	$ (32,093)	$ (24,744)

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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