Changes in Accumulated Other Comprehensive Loss by Component, Net of Tax (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	$ 1,447,971	$ 1,346,415	$ 1,489,098	$ 1,300,903
Other comprehensive income (loss) before reclassifications	(6,589)	(7,888)	(10,210)	(15,937)
Amounts reclassified from accumulated other comprehensive income (loss)	19		26	(13)
Total other comprehensive loss	(6,570)	(7,888)	(10,184)	(15,950)
Ending Balance	1,361,404	1,443,672	1,361,404	1,443,672
Foreign Currency Translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(30,725)	(18,309)	(26,925)	(10,340)
Other comprehensive income (loss) before reclassifications	(6,771)	(7,881)	(10,571)	(15,850)
Total other comprehensive loss	(6,771)	(7,881)	(10,571)	(15,850)
Ending Balance	(37,496)	(26,190)	(37,496)	(26,190)
Unrealized Gains and (Losses) on available- for-Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	8	(404)	(178)	(311)
Other comprehensive income (loss) before reclassifications	182	(7)	361	(87)
Amounts reclassified from accumulated other comprehensive income (loss)	19		26	(13)
Total other comprehensive loss	201	(7)	387	(100)
Ending Balance	209	(411)	209	(411)
Accumulated Other Comprehensive Loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Beginning Balance	(30,717)	(18,713)	(27,103)	(10,651)
Ending Balance	$ (37,287)	$ (26,601)	$ (37,287)	$ (26,601)

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

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