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401(k) Plan (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Jan. 31, 2019	Jan. 31, 2018	Jan. 31, 2017
Retirement Benefits [Abstract]
Contributions by employer	$ 28	$ 15	$ 6

X

- References

No definition available.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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