v3.22.0.1

Summary of Significant Accounting Policies - Stock-based Compensation (Details) | 12 Months Ended
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Dec. 31, 2021
2012 Employee Stock Purchase Plan |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
Award offering period | 6 months

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- Definition Share-based Compensation Arrangement by Share-based Payment Award, Purchase Offering Period + References No definition available. + Details
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Namespace Prefix: | now_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_PlanNameAxis=now_TwoThousandTwelveEmployeeStockPurchasePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |