Fair Value Measurements - Contractual Maturities of Debt Securities (Details) $ in Millions	Jan. 27, 2019 USD ($)
Contractual Maturities of Debt Securities, Amortized Cost
Amortized cost, due in one year or less	$ 4.0
Contractual Maturities of Debt Securities, Fair Value
Fair value, due in one year or less	$ 4.0

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

No definition available.

Name:	us-gaap_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant