Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance at beginning of period			$ 1,120,689	$ 1,021,236
Comprehensive income	$ 92,046	$ 85,807	103,943	74,889
Equity awards exercised/vested, net			56	1,532
Share-based compensation expense			14,876	15,362
Adjustments related to tax withholding for share-based compensation			(4,843)	(6,114)
Other			(38)	27
ASC 606 cumulative effect to retained earnings opening balance			(53,728)
Balance at end of period	$ 1,180,955	$ 1,106,932	$ 1,180,955	$ 1,106,932

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount of the related income tax effect of a cumulative effect on retained earnings.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of cash outflow to satisfy an employee's income tax withholding obligation as part of a net-share settlement of a share-based award.

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Amount of cash inflow from exercise of stock options granted under share-based compensation arrangement.

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The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which are attributable to the parent. The amount of the economic entity's stockholders' equity attributable to the parent excludes the amount of stockholders' equity which is allocable to that ownership interest in subsidiary equity which is not attributable to the parent (noncontrolling interest, minority interest). This excludes temporary equity and is sometimes called permanent equity.

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This element represents movements included in the statement of changes in stockholders' equity which are not separately disclosed or provided for elsewhere in the taxonomy.

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